Nuclear translocation of the Y‐box binding protein by ultraviolet irradiation

Abstract

The Y‐box binding protein, YB‐1, is a member of a DNA binding protein family with a structurally and functionally conserved cold shock domain. Using Western blotting and immunohistochemical methods, larger amounts of YB‐1 were detected in the cytosol, particularly at the perinuclear region, than in the nucleus of human cancer cells. UV irradiation increased accumulation of YB‐1 in the nucleus at 20 min and thereafter. This translocation of YB‐1 into the nucleus by UV irradiation was blocked by the protein kinase inhibitor H‐7, but not HA‐1004. Both green fluorescent protein (GFP)‐YB‐1 and GFP‐YB‐1C with the C‐terminus (248–317) of YB‐1 were located mainly in the cytosol, but GFP‐YB‐1ΔC with a deletion at the C‐terminus of YB‐1 was located in the nucleus. YB‐1 is translocated into the nucleus by UV irradiation, possibly through a protein kinase C‐mediated signal transduction pathway, and the C‐terminal region of YB‐1 might be important for cytoplasmic retention of YB‐1.