Cell cycle checkpoint signaling through the ATM and ATR kinases

In the paper

“Under identical experimental conditions, ATM did not enter into nuclear foci in cells damaged with IR or other DNA-damaging agents.”

In the paper

“A peptide containing these sites was phosphorylated at a higher rate by ATR than by ATM (Kim et al. 1999), and we have found that a GST-hRad17 fusion protein is a significantly better substrate for ATR than for ATM (Bao et al. 2001; R.S. Tibbetts and R.T. Abraham, unpubl.).”

What the sources say

• Not checked yetcites Bao et al. 2001
• Not checked yetcites R.S. Tibbetts and R.T. Abraham, unpubl.

In the paper

“On the other hand, our group has failed to detect any increases in the in vitro kinase activity of ATR after treatment of cells with various genotoxic agents, including IR and UV light (R.S. Tibbetts and R.T. Abraham, unpubl.).”

What the sources say

• Not checked yetcites R.S. Tibbetts and R.T. Abraham, unpubl.

In the paper

“Disruption of this pathway yields the radioresistant DNA synthesis (RDS) phenotype.”

In the paper

“The amino-terminal cross-hatched box indicates a functionally undefined region of homology between ATM (residues 1493-1773) and ATR (residues 1191-1463).”

In the paper

“No significant homology was detected between the predicted FATC domains of these two proteins.”

In the paper

“Hence, loss of either of two biochemically connected checkpoint kinases, ATM or Chk2, paradoxically increases the resistance of immature (CD4 + CD8 + ) T cells to ionizing radiation (IR)-induced apoptosis (Xu and Baltimore 1996;Hirao et al. 2000).”

What the sources say

• Not checked yetcites Xu and Baltimore 1996
• Not checked yetcites Hirao et al. 2000

In the paper

“The catalytic domains (∼300 amino acids) of the PIKK family members are located near their carboxyl termini, and are flanked by two loosely conserved domains termed FAT (FRAP/ATM/TRRAP) and FATC (the “C” indicates carboxy-terminal) (Bosotti et al. 2000).”

What the sources say

• Not checked yetcites Bosotti et al. 2000

In the paper

“First, the protein kinase activity of ATM, but not of ATR or DNA-PK, is quite sensitive to inhibition by the nonionic detergents (e.g., Triton X-100, NP-40) commonly used to prepare whole cell or nuclear extracts (Gottlieb and Jackson 1993;Sarkaria et al. 1998Sarkaria et al. , 1999;;Yavuzer et al. 1998).”

What the sources say

• Not checked yetcites Gottlieb and Jackson 1993
• Not checked yetcites Sarkaria et al. 1998
• Not checked yetcites Yavuzer et al. 1998

In the paper

“Interestingly, all of the PIKKs characterized to date, mammalian or otherwise, function as S/T-Q-directed kinases, with the no-table exception of the yeast and mammalian TOR proteins.”

In the paper

“As mentioned earlier, ATM and ATR belong to a structurally unique family of protein serine-threonine kinases whose catalytic domains share a clear evolutionary relationship with those of mammalian and yeast phosphoinositide 3-kinases (Hunter 1995;Zakian 1995;Tibbetts and Abraham 2000).”

What the sources say

• Not checked yetcites Hunter 1995
• Not checked yetcites Zakian 1995
• Not checked yetcites Tibbetts and Abraham 2000

In the paper

“One of the cloned cDNAs, termed ATM, attracted widespread attention, because mutations in this gene underlie the heritable chromosomal instability disorder, ataxia-telangiectasia (A-T) (Savitsky et al. 1995).”

What the sources say

• Not checked yetcites Savitsky et al. 1995

In the paper

“Subsequent studies revealed that biochemically purified ATM could be captured from solution by immobilized DNA fragments (for review, see Durocher and Jackson 2001).”

What the sources say

• Not checked yetcites Durocher and Jackson 2001

In the paper

“This prediction held true for ATM, as the protein kinase activity of the immunoprecipitated enzyme increases several fold within 1 h after cellular exposure to IR or radiomimetic agents (Banin et al. 1998;Canman et al. 1998).”

What the sources say

• Not checked yetcites Banin et al. 1998
• Not checked yetcites Canman et al. 1998

In the paper

“A peptide containing these sites was phosphorylated at a higher rate by ATR than by ATM (Kim et al. 1999), and we have found that a GST-hRad17 fusion protein is a significantly better substrate for ATR than for ATM (Bao et al. 2001; R.S. Tibbetts and R.T. Abraham, unpubl.).”

What the sources say

• Not checked yetcites Kim et al. 1999

In the paper

“In general, the specific activity of ATR toward most substrates in vitro is significantly lower than that displayed by ATM (Canman et al. 1998; R.S. Tibbetts and R.T. Abraham, unpubl.).”

What the sources say

• Not checked yetcites Canman et al. 1998
• Not checked yetcites R.S. Tibbetts and R.T. Abraham, unpubl.

In the paper

“One notable exception is the human checkpoint protein, hRad17, which contains two S-Q sites that are phosphorylated by both ATM and ATR in immune complex kinase assays.”

What the sources say

• Not checked yetcites Kim et al. 1999

In the paper

“The available evidence suggests that the consensus sequence for phosphorylation by ATR overlaps extensively with that defined for ATM (Kim et al. 1999).”

What the sources say

• Not checked yetcites Kim et al. 1999

In the paper

“However, immunofluorescence microscopy revealed that ATR responded to DNA damage by undergoing a dramatic shift in intranuclear localization, from diffuse to focal in nature (Tibbetts et al. 2000; see below for discussion).”

What the sources say

• Not checked yetcites Tibbetts et al. 2000

In the paper

“Remarkably, the specific kinase activity of the DNA-binding subpopulation of Xatr molecules was 10-to 20-fold higher than that of Xatr immunoprecipitated directly from the egg cytosol.”

What the sources say

• Not checked yetcites Guo et al. 2000

In the paper

“Despite the seeming overlap, the emerging picture suggests that the checkpoint signaling functions of ATM and ATR are far from redundant-a conclusion that should become apparent as we march through the G 1 , S, and G 2 checkpoints in the following sections.”

In the paper

“Although the empirical approach has been rewarding, the inevitable outcome has been that the list of documented ATR substrates overlaps largely, if not entirely, with that linked to ATM.”

In the paper

“Nonetheless, these results are consistent with the notion that ATM and ATR are capable of interacting directly with DNA.”

In the paper

“In addition to ATM, the members of the BASC include the mismatch repair proteins, MLH1, MSH2, and MSH6, the Bloom's syndrome helicase (BLM), and the Mre11-Rad50-NBS1 complex.”

What the sources say

• Not checked yetcites Wang et al. 2000 source

In the paper

“Indeed, gel filtration analyses indicate that both ATM and ATR are constitutive residents of very high molecular weight (M R , >2 × 10 6 D) protein complexes in mammalian cells (Wright et al. 1998;Shiloh 2001).”

What the sources say

• Not checked yetcites Wright et al. 1998
• Not checked yetcites Shiloh 2001

In the paper

“It is important to recognize that the BASC is likely not a single entity, but rather a dynamic collection of protein complexes whose compositions change with the type of DNA damage, location relative to the damaged site, and time after initiating genetic insult.”

In the paper

“The association of ATM with free DNA ends was also visualized directly by atomic force microscopy (Smith et al. 1999).”

What the sources say

• Not checked yetcites Smith et al. 1999

In the paper

“Although p53 exerts a pervasive influence on checkpoint functions during the mammalian cell cycle, the G 1 checkpoint represents the only case in which loss of p53 leads to total checkpoint abrogation”

What the sources say

• Not checked yetcites Ko and Prives 1996
• Not checked yetcites Giaccia and Kastan 1998
• Not checked yetcites North and Hainaut 2000

In the paper

“Similarly, studies in the Xenopus model system indicate that ATR binds to DNA, although specific DNA end-binding activity was not investigated (Guo et al. 2000).”

What the sources say

• Not checked yetcites Guo et al. 2000

In the paper

“Subsequent studies showed that ATR was also capable of phosphorylating p53 at Ser 15 in immune complex kinase assays”

What the sources say

• Not checked yetcites Hall-Jackson et al. 1999
• Not checked yetcites Lakin et al. 1999
• Not checked yetcites Tibbetts et al. 1999

In the paper

“In addition to p21, the activated form of p53 stimulates the expression of a large panel of genes, which, depending on the cellular context and type of initiating insult, may modulate intracellular redox status, or induce the host cell to undergo apoptosis”

What the sources say

• Not checked yetcites Yu et al. 1999

In the paper

“These studies pinpointed a single serine residue (Ser 15) in the amino-terminal region of p53 as a phosphorylation site for the ATM kinase in vitro.”

What the sources say

• Not checked yetcites Banin et al. 1998
• Not checked yetcites Canman et al. 1998

In the paper

“A link between ATM and p53 was predicted on the basis of earlier studies, which demonstrated that A-T cells exhibited a delayed and reduced level of p53 protein induction following exposure to IR”

What the sources say

• Not checked yetcites Kastan et al. 1992
• Not checked yetcites Lu and Lane 1993

In the paper

“It appears that Ser 395 phosphorylation favors stabilization of p53 by interfering with the shuttling activity of MDM2, which normally exports p53 out of the nucleus for proteosomal degradation in the cytoplasm.”

What the sources say

• Not checked yetcites Maya et al. 2001

In the paper

“This pattern of dual regulation of substrate phosphorylation by ATM and ATR in cells exposed to different forms of genotoxic stress has become a recurrent theme in the checkpoint-signaling field.”

In the paper

“The presence of phosphates at Ser 15 and Ser 18 reduces the avidity of full-length p53 for MDM2 by approximately threefold.”

What the sources say

• Not checked yetcites Dumaz et al. 1999

In the paper

“and hChk2, in turn, phosphorylates yet another amino-terminal Ser residue (Ser 20) in p53”

What the sources say

• Not checked yetcites Chehab et al. 2000 source
• Not checked yetcites Hirao et al. 2000
• Not checked yetcites Shieh et al. 2000 source

In the paper

“ATM activates hChk2 by phosphorylating an amino terminal Thr residue (Thr 68)”

What the sources say

• Not checked yetcites Ahn et al. 2000
• Not checked yetcites Melchionna et al. 2000

In the paper

“Ser 395 in this sequence was identified as a phosphorylation site for ATM, both in vitro and in intact cells.”

What the sources say

• Not checked yetcites Maya et al. 2001

In the paper

“Of the PIKK family members, ATM represents the primary responder to IRor radiomimetic agent-induced DNA damage.”

In the paper

“On the other hand, ATR takes on the front-line signaling responsibilities when cells are challenged with other forms of genotoxic stress, such as UV light exposure or treatment with agents that interfere with DNA replication (aphidicolin, hydroxyurea; HU).”

In the paper

“Indeed, Dumaz et al. (1999) have shown that Ser 15 phosphorylation greatly enhances the subsequent phosphorylation of p53 at Ser 18 by casein kinase I, at least under test-tube assay conditions with purified proteins.”

What the sources say

• Not checked yetcites Dumaz et al. 1999

In the paper

“DNA damage detected during S phase is apt to be repaired precisely via homologous recombination mechanisms involving sister chromatids”

What the sources say

• Not checked yetcites Johnson and Jasin 2000

In the paper

“These findings demonstrate that ATM establishes multiple regulatory contacts with p53 during the activation of the G 1 checkpoint by DNA dsbs”

In the paper

“The physiological relevance of hChk2 in the regulation of p53 is supported by the finding that lossof-function mutations in hChk2 can give rise to a variant form of Li-Fraumeni syndrome”

What the sources say

• Not checked yetcites Bell et al. 1999

In the paper

“The canonical checkpoint defect displayed by A-T cells is radioresistant DNA synthesis (RDS; Painter and Young 1980).”

What the sources say

• Not checked yetcites Painter and Young 1980

In the paper

“Indeed, studies in bacteria suggest that S phase cells rely heavily on homologous recombination to restart stalled replication forks, even in the absence of genotoxic agents”

What the sources say

• Not checked yetcites Cox 1999
• Not checked yetcites Cox et al. 2000

In the paper

“Although loss of ATM function is causally related to RDS, the downstream effectors in this S-phase pathway checkpoint pathway have largely eluded identification”

In the paper

“Treatment of cells with wortmannin, at drug concentrations that abrogate ATM kinase activity, also induces RDS in normal (ATM-proficient) cells”

What the sources say

• Not checked yetcites Sarkaria et al. 1998

In the paper

“An intriguing report now shows that the surveillance functions of the ATM-hChk2 pathway are not confined to G 1 phase”

What the sources say

• Not checked yetcites Falck et al. 2001

In the paper

“Genetic manipulations that disrupt any step in the pathway from hChk2 to cyclin A•cdk2 also give rise to the RDS phenotype.”

What the sources say

• Not checked yetcites Falck et al. 2001

In the paper

“In normal cells, exposure to IR provokes a rapid but reversible decrease in DNA synthesis, which reflects decreases in the rates of both replication origin firing and DNA strand elongation”

What the sources say

• Not checked yetcites Painter and Young 1980

In the paper

“Overexpression of the previously described ATR KI mutant in SV40-transformed (but ATM-positive) human fibroblasts also induces RDS”

What the sources say

• Not checked yetcites Cliby et al. 1998

In the paper

“The down-regulation of Cdc25A interferes with the timely activation of cyclin A•cdk2, which is a requisite event for the firing of early origins of replication during S phase”

What the sources say

• Not checked yetcites Donaldson and Blow 1999
• Not checked yetcites Takisawa et al. 2000

In the paper

“Accumulating evidence suggests that BRCA1 is a critically important caretaker of the replicating genome in vertebrate cells.”

What the sources say

• Not checked yetcites Scully and Livingston 2000
• Not checked yetcites Scully et al. 2000
• Not checked yetcites Xu et al. 2001

In the paper

“Recent findings position ATM and ATR as critical upstream modulators of the breast cancer susceptibility protein, BRCA1”

What the sources say

• Not checked yetcites Wang et al. 2000 source

In the paper

“A second participant in the DNA damage-induced Sphase checkpoint is NBS1 (also termed nibrin), the product of the gene mutated in the human chromosomal instability disorder, NBS”

What the sources say

• Not checked yetcites Shiloh 1997
• Not checked yetcites Carney 1999
• Not checked yetcites Petrini 1999

In the paper

“Like the NBS1 complex, BRCA1 participates in both checkpoint and repair pathways in DNA-damaged cells”

What the sources say

• Not checked yetcites Scully and Livingston 2000
• Not checked yetcites Scully et al. 2000
• Not checked yetcites Xu et al. 2001

In the paper

“Nonetheless, the functional linkage between ATM and the NBS1-Mre11-Rad50 complex becomes even more compelling with the discovery that hypomorphic Mre11 alleles give rise to an A-T-like disorder in humans”

What the sources say

• Not checked yetcites Stewart et al. 1999

In the paper

“A central premise of modern cancer cell biology is that cancer development is a hyperevolutionary process fueled by genetic instability (Hartwell and Kastan 1994;Weinert 1997;Lengauer et al. 1998;Cahill et al. 1999).”

What the sources say

• Not checked yetcites Hartwell and Kastan 1994
• Not checked yetcites Weinert 1997
• Not checked yetcites Lengauer et al. 1998

In the paper

“The finding that caffeine, an inhibitor of mammalian ATM and ATR (Sarkaria et al. 1999), selectively sensitizes p53-deficient tumor cells to killing by IR lends credibility to this therapeutic strategy (Powell et al. 1995;Yao et al. 1996).”

What the sources say

• Not checked yetcites Sarkaria et al. 1999

In the paper

“The identification of ATM as a key regulator of p53 in cells that have incurred DNA dsbs not only links ATM to the G 1 checkpoint, but also suggests that ATM participates directly in making life and death decisions in certain cell types, particularly thymocytes and early-stage neurons.”

In the paper

“Several groups have documented that BRCA1 is phosphorylated in vitro on multiple sites by the ATM and ATR kinases”

What the sources say

• Not checked yetcites Cortez et al. 1999
• Not checked yetcites Chen 2000
• Not checked yetcites Gatei et al. 2000a

In the paper

“Studies of the DNA damage responses in BRCA1-deficient cells are focusing increasing attention on the role of BRCA1 in promoting highfidelity DNA repair through homologous recombination between sister chromatids”

What the sources say

• Not checked yetcites Moynahan et al. 1999
• Not checked yetcites Scully et al. 2000

In the paper

“In A-T patients, disruption of the p53-dependent pathways that would normally direct irreparably damaged cells to undergo apoptosis during embryonic or early postnatal life may sow the seeds for the neurodegeneration and cancer predisposition that are so characteristic of this disease.”

In the paper

“The identification of ATM as a key regulator of p53 in cells that have incurred DNA dsbs not only links ATM to the G 1 checkpoint, but also suggests that ATM participates directly in making life and death decisions in certain cell types, particularly thymocytes and early-stage neurons.”

In the paper

“The right branch of the pathway is activated by DNA damage during the G 2 phase itself, and depends largely on the activation of ATM.”

In the paper

“Complete loss of this pathway is likely incompatible with viability, even in the absence of genotoxic agent-induced DNA damage.”

In the paper

“The operation of this pathway prevents mitotic catastrophe that results from incomplete or inaccurate DNA replication, and orchestrates high-fidelity DNA repair through homologous recombination.”

In the paper

“ATR may influence Ser 20 phosphorylation through activation of Chk1.”

In the paper

“The operation of this pathway prevents mitotic catastrophe that results from incomplete or inaccurate DNA replication, and orchestrates high-fidelity DNA repair through homologous recombination.”

In the paper

“The left branch of this pathway is activated when cells incur DNA damage before completion of S phase, and is governed primarily by ATR.”

In the paper

“The ATM-dependent pathway shown in the left panel is initiated by the presence of a DNA dsb in an S-phase cell.”

In the paper

“In the right panel, the checkpoint pathway is triggered by intrinsic events or environmental insults that impair replication fork progression during S phase.The pathway is governed primarily by ATR, and may use members of the Rad family of checkpoint proteins as damage sensors and as scaffolds for the assembly of checkpoint signaling complexes.”

In the paper

“The finding that caffeine, an inhibitor of mammalian ATM and ATR (Sarkaria et al. 1999), selectively sensitizes p53-deficient tumor cells to killing by IR lends credibility to this therapeutic strategy (Powell et al. 1995;Yao et al. 1996).”

What the sources say

• Not checked yetcites Powell et al. 1995
• Not checked yetcites Yao et al. 1996

In the paper

“Cells that have incurred DNA double-strand breaks (dsbs) during G 1 phase activate p53 primarily via an ATM-dependent pathway.”

In the paper

“The checkpoint response leads to the proteosome-mediated degradation of Cdc25A, and, in turn, the failure to maintain activation of cyclin•cdk2 complexes and a resultant inhibition of DNA synthesis.”

In the paper

“ATM regulates p53 accumulation by indirect pathways involving the Chk2-mediated phosphorylation of Ser 20 on p53, by promoting casein kinase-I-dependent phosphorylation of Ser 18 (not shown), and by directly phosphorylating MDM2 on Ser 395 (see text for details).”

In the paper

“In cells that express both ATM and ATR, the activation of p53 is reinforced and maintained by ATR (pathway indicated by dotted lines).”

In the paper

“ATM regulates p53 accumulation by indirect pathways involving the Chk2-mediated phosphorylation of Ser 20 on p53, by promoting casein kinase-I-dependent phosphorylation of Ser 18 (not shown), and by directly phosphorylating MDM2 on Ser 395 (see text for details).”

In the paper

“ATM regulates p53 accumulation by indirect pathways involving the Chk2-mediated phosphorylation of Ser 20 on p53, by promoting casein kinase-I-dependent phosphorylation of Ser 18 (not shown), and by directly phosphorylating MDM2 on Ser 395 (see text for details).”