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Cited by 735Cancer-related Molecular PathwaysCell death mechanisms and regulationDNA Repair Mechanisms

p53 levels, functional domains, and DNA damage determine the extent of the apoptotic response of tumor cells.

Open access
Chen, X, Ko, L J, Jayaraman, L, Prives, C·1996·Genes & Development
DOI 10.1101/gad.10.19.2438
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Abstract

It is well established that induction of the p53 tumor suppressor protein in cells can lead to either cell cycle arrest or apoptosis. To further understand features of p53 that contribute to these cell responses several p53-null Saos2 and H1299 cell lines were generated that express wild-type or mutant forms of p53, or the cyclin-dependent kinase inhibitor p21/WAF1, under a tetracycline-regulated promoter. Our results show that the cellular level of p53 can dictate the response of the cell such that lower levels of p53 result in arrest whereas higher levels result in apoptosis; nevertheless, DNA damage can heighten the apoptotic response to p53 without altering the protein level of p53 in cells. We also demonstrate that arrest and apoptosis are two genetically separable functions of p53 because a transcriptionally incompetent p53 can induce apoptosis but not arrest, whereas induction of p21/WAF1, which is a major transcriptional target of p53, can induce arrest but not apoptosis. Finally, we show that a full apoptotic response to p53 requires both its amino and carboxyl terminus, and our data suggest that there is synergism between transcription-dependent and -independent functions of p53 in apoptosis. Thus, there are multiple independent cellular responses to p53 that together may account for the extraordinarily high frequency of p53 mutations in diverse types of human tumors. The implications of these results are discussed and a model is proposed.

AI snapshot

Written from the paper’s full text.

TL;DR

In tetracycline-inducible p53-null Saos2 and H1299 cells, p53 protein level determines whether cells arrest or undergo apoptosis, and camptothecin-induced DNA damage sensitizes low-p53 cells to apoptosis without raising p53 levels. Arrest and apoptosis are genetically separable: p21 induces arrest but not apoptosis, transactivation-deficient p53 can induce delayed apoptosis, and a full apoptotic response requires both amino- and carboxyl-terminal domains.

Key findings

  • In Saos2 p53-7 cells, high induced p53 caused cell death: by 3 days only 10% of cells survived, and sub-G1 cells rose to 25% at 2 days and >60% at 3 days; low-producer p53-13 cells had ~25–50% of p53-7 p53 levels, showed slowed growth and S-phase reduction from 31% to 15% by day 1, but no sub-G1 cells.
  • Camptothecin treatment of p53-13 cells increased apoptosis when p53 was induced, with no discernible increase in p53 protein; even without p53 induction, CPT caused a modest p53-independent apoptotic response.
  • p21 induction in p21S4 cells reduced S-phase cells from 32% to 14% after 3 days and caused arrest in G1 and G2 with no apoptosis; p53(gln22/ser23) did not induce p21 or arrest but reproducibly induced delayed, reduced apoptosis.
  • p53(AC30) induced p21 and arrest but only weak delayed apoptosis; p53(AN96), p53(ser249), and p53(his175) were inert for apoptosis; p53(gln22/ser23AC30) was completely inert for apoptosis or growth arrest in H1299 cells, indicating both amino- and carboxyl termini are required for a full apoptotic response.

Methods

  • Generated tetracycline-regulated inducible cell lines in p53-null Saos2 and H1299 cells expressing wild-type p53, mutant p53 forms [p53(gln22/ser23), p53(AN22), p53(AN96), p53(AC30), p53(gln22/ser23AC30), p53(his175), p53(ser249)], or p21.
  • Used Western blotting for p53, p21, actin, Bax, and Bcl-2; growth curves; and flow cytometric DNA-content analysis for cell-cycle distribution and sub-G1 apoptotic cells.
  • Treated cells with camptothecin to induce DNA damage and compared responses in the presence or absence of tetracycline; RKO cells were used as a DNA-damage/p53-induction control.

Limitations

  • Stated: the authors cannot rule out that other p53 targets also contribute to arrest; whether p53(AN22) is fully comparable to wild-type p53 is not yet established; it remains to be determined whether CPT-p53 cooperation occurs in cells other than Saos2; some results are preliminary or data not shown.
  • Evident: the conclusions rely on clonal tetracycline-inducible Saos2 and H1299 cell lines and on growth/FACS assays, with no in vivo data or independent validation of all mutant lines shown.
  • Evident: the text contains many “data not shown” claims and OCR/formatting gaps, limiting verification of some supporting results.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1101/gad.10.19.2438

Cites

65 of 65 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 43 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Induction of p53(AN96) had no measurable effect on cell growth or arrest.

    “Upon withdrawal of tetracycline, p53(&N96)-5 cells expressed markedly higher levels of truncated p53 than in the high producer wild-type p53 cell line, p53-7 (data not shown), yet induction of p53(AN96 had no measurable effect on cell growth or arrest (Table 1 and Fig. 8).”
    Quote in the paperSubstantial claim
  • Findingown data

    p21 expression was markedly increased in both p53-13 and p53-7 cells after removal of tetracycline.

    “Consistent with these results p21 expression was markedly increased in both p53-13 and p53-7 cells after removal of tetracycline (Fig. 2A).”
    Quote in the paperSubstantial claim
  • Findingown data

    Treatment of RKO cells with CPT results in a significant induction of p53 protein levels.

    “Moreover, as shown in Figure 1A, we have confirmed that treament of RKO cells with CPT results in a significant induction of p53 protein levels.”
    Quote in the paperNot a substantial claim
  • Findingown data

    The level of p53 in the p53-7 Saos2 cell line can determine whether the cells undergo growth arrest or apoptosis.

    “We conclude from these data that the level of p53 in the p53-7 Saos2 cell line can determine whether the cells undergo growth arrest or apoptosis.”
    Quote in the paperSubstantial claim
  • Findingown data

    The growth curves and FACS profiles of cells expressing p21 were similar to those of cells expressing lower levels of p53.

    “The growth curves and FACS profiles of cells expressing p21 were similar to those expressing lower levels of p53 (cf.Figs. 2 and 5).”
    Quote in the paperSubstantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 16

  • May combine two claims.

    Findingown data

    When p53 was induced in CPT-treated p53-13 cells, there was a significant increase in the number of apoptotic cells, and yet no discernable increase of p53 protein levels.

    “Unexpectedly, however, when p53 was induced in CPTtreated p53-13 cells there was a significant increase in the number of apoptotic cells (Fig. 4B), and yet no discernable increase of p53 protein levels (Fig. 4A).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    DNA histogram analysis of induced p53-7 cells showed that 1 day after tetracycline withdrawal the percentage of cells in S phase was reduced from 14% to 5%, and the percentage of cells in G2 was increased from 14% to 23%, suggesting a transient G2 arrest in at least a fraction of the cells.

    “DNA histogram analysis of induced p53-7 cells (Fig. 1C) showed that 1 day after tetracycline withdrawal the percentage of cells in S phase was reduced from 14% to 5%, and the percentage of cells in G 2 was increased from 14% to 23%, suggesting that a transient G2 arrest had occurred in at least a fraction of the cells; at this time point little or no sub-G1 content cells were scored.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Upon maximal p21 induction, p21S4 cells underwent cell-cycle arrest with no evidence of apoptosis.

    “However, upon m a x i m a l p21 induction, p21S4 cells underwent cell-cycle arrest with no evidence of apoptosis (Fig. 5B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The transcriptionally defective p53 mutant p53(gln22/ser23) cannot induce p21 or cell-cycle arrest, yet it can induce apoptosis, albeit to a lesser extent.

    “the transcriptionally defective p53 mutant p53(gln22/ser23) can not induce p21 (nor can it effect a cell-cycle arrest) and yet it can induce apoptosis, albeit to a lesser extent.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The p53 mutant p53(gln22/ser23) is transcriptionally defective.

  • May combine two claims.

    Findingown data

    Uninduced p53-7 cells continued to grow with a doubling time of ~48 hr, whereas p53-expressing cells started to die within 2 days, and by 3 days only 10% of the cells survived.

    “The uninduced cells continued to grow with a doubling time of -48 hr, whereas the p53 expressing cells started to die within 2 days (as determined by reduced cell count), and by 3 days, only 10% of the cells survived.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    p53(AC30) can induce apoptosis, but far more weakly than full-length p53, suggesting that the carboxy terminal 30 amino acids of p53 are required for efficient apoptotic activity.

    “Therefore, in this cell line and in others (data not shown), p53(AC30) can induce apoptosis, but far more weakly than full-length p53, suggesting that the carboxy terminal 30 amino acids of p53 are required for efficient apoptotic activity.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    p53-13 cells exhibit a significant arrest in both G1 and G2, but no apoptosis.

    “p53-13 cells, therefore, exhibit a significant arrest in both G1 and G2, but no apoptosis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In H1299 cells, one high p53 producer cell line underwent apoptosis after induction while a low producer cell line underwent arrest.

    “As was observed with Saos2 cells, one high p53 producer H1299 cell line underwent apoptosis after induction while a low producer H1299 cell line underwent Regulation of p53-dependent apoptosis Time of p53 expression (D) 0D 1D 2D 3D 4D 49.76 57,12 59.64 58.33 50,34 24.41 16.13 13,57 10,86 14.48 22.85 24.80 24.28 22.29 20.15 2.98 1,95 2.51 8.52 15,04 i Tet fo, 2 day, .. arrest.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Even without p53 induction, p53-13 cells treated with CPT showed a modest apoptotic response, suggesting that Saos2 cells can undergo DNA damage-associated apoptosis in a p53-independent manner.

    “When p53-13 cells were treated with increasing amounts of CPT in the presence or absence of tetracycline we observed that even without p53 induction there was a modest apoptotic response to CPT, sug-gesting that Saos2 cells can undergo DNA damage-associated apoptosis in a p53-independent manner (Fig. 4B).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Despite comparable p21 induction in p21- and p53-inducible cell lines, the high producer p53-7 cells underwent both arrest and apoptosis.

    “Despite the fact that p21 was induced to comparable levels in p21-and p53-inducible cell lines, the high producer p53-7 cells underwent both arrest and apoptosis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The amount of detectable induced p53 protein in p53-7 cells was substantively less than that induced in DNA damaged human RKO cells that contain wild-type p53, demonstrating that the level of p53 expressed in the Saos2 cell line is within the physiological range.

    “Note that the amount of detectable induced p53 protein in p53-7 cells, however, was substantively less than that induced in DNA damaged human RKO cells that contain wild-type p53 (Kastan et al. 1992), demonstrating that the level of p53 expressed in the Saos2 cell line is within the physiological range.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Kastan et al. 1992

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    p53-13 cells showed substantially slowed cell growth but no reduction in cell number and no sub-G1 DNA content.

    “Although p53-13 cells showed substantially slowed cell growth, there was in contrast with p53-7 cells, no reduction in cell number (Fig. 2B) nor did cells with sub-G1 DNA content appear (Figure 2G).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    By 2 days after induction, 25% of p53-7 cells had a sub-G1 DNA content, and at 3 days after induction >60% of the cells had sub-G1 DNA content indicating apoptotic death.

    “By 2 days, however, 25% of the cells had a sub-G1 DNA content and at 3 days after induction >60% of the cells had sub-G1 DNA content indicating apoptotic death, with the remaining cells primarily arrested in G~.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Induction of Bax RNA or protein was not observed in Saos2 cells, implying that other p53 responsive genes are activated in these cells.

    “Although the Bax gene is an obvious candidate for an apoptotic p53 target gene, induction of Bax RNA or protein was not observed in Saos2 cells (data not shown), implying that other p53 responsive genes are activated in these cells.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    In cells expressing p21 or lower levels of p53, a dramatically reduced growth rate was accompanied by arrest in both G1 and G2.

    “In each case a dramatically reduced growth rate was accompanied by arrest in both G1 and G 2.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    p53(gln22/ser23) reproducibly induced cell death in 22/23-4 cells, although to a lesser extent and with delayed kinetics as compared with wild-type p53.

    “Nevertheless, in these cells p53(gln22/ser23)reproducibly induced cell death (Fig. 6), although to a lesser extent and with delayed kinetics as compared with wild-type p53.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Induction of a delayed apoptosis but not arrest by p53 transactivation defective mutant p53(gln22/ser23).

    “Induction of a delayed apoptosis but not arrest by p53 transactivation defective mutant p53 (gln22/ser23).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The p53 mutant p53(gln22/ser23) is transcriptionally defective.

  • May combine two claims.

    Findingown data

    A low level of p53 is not sufficient to induce apoptosis in Saos2 cells, but it can sensitize cells to undergo apoptosis following CPT-induced DNA damage.

    “Even though a low level of p53 is not sufficient to induce apoptosis in Saos2 cells, it can sensitize cells to undergo apoptosis following CPT-induced DNA damage.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Several cellular and viral proteins contribute to the propensity of cells to undergo either arrest or apoptosis.

    “several cellular and viral proteins contribute to the propensity of cells to undergo either response [for review, see Fisher i994; White 1996).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Fisher i994

      Not checked in the free run.

    • cites White 1996

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Down-regulation of IGF-1 or the IGF-1 receptor is correlated with the apoptotic response.

    “Down-regulation of IGF-1 or the IGF-1 receptor is correlated with the apoptotic response (Baserga 1994).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Baserga 1994

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    IGFBP-3 is a p53 target and an antagonist of insulin-like growth factor-1 (IGF-1).

    “A second p53 target that might influence apoptosis is IGFBP-3 (Buckbinder et al. 1995), which is an antagonist of insulin-like growth factor-1 (IGF-II (Baserga 1994).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Buckbinder et al. 1995

      Not checked in the free run.

    • cites Baserga 1994

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Deletion of the carboxy-terminal 30 amino acids of p53 has striking stimulatory effects on the ability of the protein to bind to DNA in vitro.

    “Moreover, deletion of the carboxy-terminal 30 amino acids of p53 has striking stimulatory effects on the ability of the protein to bind to DNA in vitro (Hupp et al. 1992;Halazonetis and Kandil 1993).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Hupp et al. 1992

      Not checked in the free run.

    • cites Halazonetis and Kandil 1993

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Several recent studies have provided evidence that p53 may have a transcription-independent function in apoptosis.

    “Several recent studies have provided evidence, however, that p53 may have a transcription-independent function in apoptosis (Caelles et al. 1994;Wagner et al. 1994).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Caelles et al. 1994

      Not checked in the free run.

    • cites Wagner et al. 1994

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    The bax product dimerizes with Bcl-2 and prevents Bcl-2 from blocking apoptosis.

    “whose product dimerizes with Bcl-2 and prevents the ability of Bcl-2 to block apoptosis (Oltvai et al. 1993).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Oltvai et al. 1993

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    p21 inhibits the protein kinase activities of G1 cyclin/CDK complexes, thereby preventing phosphorylation of the retinoblastoma (RB) protein.

    “which inhibits the protein kinase activities of G1 cyclin/CDK complexes, thereby preventing phosphorylation of the retinoblastoma (RB) protein (Slobos et al. 1994).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Slobos et al. 1994

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Different reports have provided essentially contradictory results as to the requirement for the sequence-specific transactivation function of p53 for induction of apoptosis.

    “Furthermore, different reports have provided essentially contradictory results as to the requirement for the sequence-specific transactivation function of p53 for induction of apoptosis (Haupt et al. 1995;Sabbitini et al. 1995).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Haupt et al. 1995

      Not checked in the free run.

    • cites Sabbitini et al. 1995

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The vast majority of missense mutations detected in tumors of cancer patients map to the central DNA-binding domain of p53.

    “The vast majority of the missense mutations that have been detected in tumors of cancer patients map to the central DNA-binding domain of p53 (Hollstein et al. 1991).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Hollstein et al. 1991

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    p53 is a sequence-specific transcriptional activator of genes containing p53 response elements.

    “p53 is a sequence-specific transcriptional activator of genes containing p53 response elements (for review, see Vogelstein and Kinzler 1992).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Vogelstein and Kinzler 1992

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    These residues are required for the interaction of the activation domain with TATA-box binding protein associated factors (TAFs).

    “This is presumably the case because these residues are required for the interaction of the activation domain with TATA-box binding protein associated factors (TAFs) (Lu and Levine 1995;Thut et al. 1995).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Lu and Levine 1995

      Not checked in the free run.

    • cites Thut et al. 1995

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The extent of arrest at day 1 after induction of p53-7 cells was greater than that in p21 cells, suggesting that p21 may not be the sole mediator of arrest after p53 induction.

    “It is notable that the extent of arrest at day 1 after induction of p53-7 cells was greater than that in p21 cells (cf.Fig. 2B and Fig. 5B), suggesting that p21 may not be the sole mediator of arrest after p53 induction.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Because p21 induction is not correlated with p53-mediated apoptosis in the cell lines examined, there may be alternate p53 target genes involved in apoptosis that might be bound relatively weakly by p53 and would thus require more p53 protein to ensure sufficient site occupancy for transcriptional activation.

    “Because p21 induction is not correlated with p53-mediated apoptosis in the cell lines examined, there may be alternate p53 target genes involved in apoptosis that might be bound relatively weakly by p53 and would thus require more p53 protein to ensure sufficient site occupancy for transcriptional activation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Because the low p53 producer cells (p53-13) did not undergo apoptosis, p21 on its own is unable to produce an apoptotic response.

    “Because the low p53 producer cells (p53-13) did not undergo apoptosis this data thus strongly suggest that p21 on its own is unable to produce an apoptotic response.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Neither DNA binding nor the carboxy-terminal domain are sufficient for apoptosis.

    “This indicates that neither DNA binding nor the carboxy-terminal domain are sufficient for apoptosis.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    p53 and CPT cooperate in Saos2 cells to cause a strong apoptotic response, and this occurs in a manner that is independent of p53 protein accumulation.

    “Thus, p53 and CPT cooperate in Saos2 cells to cause a strong apoptotic response, and this occurs in a manner that is independent of p53 protein accumulation.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    The basal transcription factors TFIID and TFIIH each contain more than one polypeptide component that interacts with p53.

    “both of which contain more than one polypeptide component that interacts with p53.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Xiao et al. 1994

      Not checked in the free run.

    • cites Wang et al. 1995

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    p53 and TFIID cooperatively interact when both are bound to DNA.

    “Indeed, previously we reported cooperative interaction between p53 and TFIID when both were bound to DNA (Chen et al. 1993).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Chen et al. 1993

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The cellular proteins 53BP1 and 53BP2 can bind to the central core region of wild-type but not mutant p53.

    “the identification of the cellular proteins 53BP 1 and 53BP2 that can bind to the central core region of wild-type but not mutant p53 (Iwabuchi et al. 1994)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Iwabuchi et al. 1994

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    p53 might need to be bound to cognate sites in DNA, but not necessarily activating transcription, to be in the correct conformation for its role in apoptosis.

    “Therefore, our results suggest that p53 might need to be bound to cognate sites in DNA but not necessarily activating transcription for it to be in the correct conformation for its role in apoptosis.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The one feature common to tumor-derived p53 mutations is a defect in sequence-specific p53 DNA binding.

  • May combine two claims.

    Premisecitation

    Overexpressed p53 amino-terminal fragment 1-214 or carboxy-terminal fragment 319-393 can induce some degree of cell death.

    “overexpressed p53 amino-terminal fragment 1-214 (Haupt et al. 1995) or carboxy-terminal fragment 319-393 (Wang et al. 1996) can induce some degree of cell death.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Haupt et al. 1995

      Not checked in the free run.

    • cites Wang et al. 1996

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    Transcription-dependent and -independent apoptotic pathways induced by wild-type p53 and p53(AC30) or p53(gln22/ser23), respectively, cooperate to induce a full apoptotic response.

    “Because the extent and kinetics of apoptosis induced by intact wild-type p53 are far greater than those by either of p53(AC30) or p53(gln22/ser23), we propose that transcription-dependent and -independent apoptotic pathways induced by these p53 variants, respectively, cooperate to induce a full apoptotic response.”
    Quote in the paperSubstantial claim
40 of 40

  • The paper relies on this without support.

    Saos2 and H1299 cell lines are p53-null, so any p53-induced responses observed after induction are due to the introduced p53 rather than endogenous p53.

    “we chose the human osterosarcoma cell line Saos2 because they are null for p53”
    “another p53-null human cell background”

  • The paper relies on this without support.

    The tetracycline-regulated expression system itself does not alter cell-cycle progression or apoptosis apart from the induced protein.

    “under a tetracycline-regulated promoter”
    “The uninduced cells continued to grow with a doubling time of -48 hr”

  • The paper relies on this without support.

    The amount of induced p53 protein detected by immunoblot reflects the amount of functional p53 activity in the cell.

    “the amount of p53 within p53-13 cells was -25-50% of that detected in p53-7 cells”

  • The paper relies on this without support.

    The clonal cell lines selected are representative of the effects of the expressed p53 or p21 proteins and not due to clonal variation.

    “Each individual cell line used for this study was chosen from a number of clonal lines based on relative levels of protein expressed after induction.”

  • The paper relies on this without support.

    The one feature common to tumor-derived p53 mutations is a defect in sequence-specific p53 DNA binding.

    “It is well established that the one feature common to the tumor-derived p53 mutations is a defect in sequencespecific p53 DNA binding.”

  • The paper relies on this without support.

    The p53 mutant p53(gln22/ser23) is transcriptionally defective.

    “the transcriptionally defective p53 mutant p53(gln22/ser23) can not induce p21 (nor can it effect a cell-cycle arrest) and yet it can induce apoptosis, albeit to a lesser extent.”
6 of 6

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Authors
Chen, X., Ko, L. J., Jayaraman, L., & Prives, C.
Affiliations
Columbia University (US)
ORCID
Prives, C
Venue
Genes & Development
Publisher
Cold Spring Harbor Laboratory
Published
1996-10-01
Volume
10
Issue
19
Pages
2438-2451
ISSN
  • 0890-9369 (ISSN-L)
  • 1549-5477
DOI
10.1101/gad.10.19.2438
OpenAlex
W2129905922
Semantic Scholar
b0abdce5fa1e7125eb79cee669efd5c66e0b22e8
Cited by
735
References
65
Citations by year
2026: 4 · 2025: 5 · 2024: 6 · 2023: 6 · 2022: 13 · 2021: 14 · 2020: 12 · 2019: 11 · 2018: 13 · 2017: 11 · 2016: 14 · 2015: 19 · 2014: 20 · 2013: 18 · 2012: 20
Type
posted content
Language
en
Open access
Locations
  • Genes & Development (publishedVersion)
  • PubMed (publishedVersion)
  • HighWire Press Open Archive (submittedVersion)
Funders
  • National Institutes of Health (CA58316)
  • National Cancer Institute (CA 58316)
Topics
  • Health Sciences › Medicine › Oncology › Cancer-related Molecular Pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Cell death mechanisms and regulation
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › DNA Repair Mechanisms
Keywords
p53, apoptosis, cell cycle arrest, DNA damage, p21, TP53 mutation, tumor suppressor
MeSH terms
Camptothecin, Cell Cycle, Cell Division, DNA Damage, Enzyme Inhibitors, Humans, Mutation, Osteosarcoma, Tetracycline, Transcription, Genetic, Tumor Cells, Cultured, Transcriptional Activation, Tumor Suppressor Protein p53, Cyclins, Apoptosis, Carcinoma, Small Cell, Cyclin-Dependent Kinase Inhibitor p21, Topoisomerase I Inhibitors

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Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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