T. Ise et al., Transcription factor Y-box binding protein 1 binds preferentially to cisplatin-modified DNA and interacts with proliferating cell nuclear antigen, CANCER RES, 59(2), 1999, pp. 342-346
The Y-box binding protein (YB-1) binds to inverted CCAAT box sequences that
are present in the promoter region of many genes. We previously showed tha
t YB-T is overexpressed in human cancer cell lines that are resistant to ci
splatin and that the depletion of YB-l by transfection of a vector expressi
ng YB-1 antisense RNA increases the sensitivity of human cancer cells to ci
splatin. To determine whether YB-1 can bind to cisplatin-modified DNA, we f
used YB-1 cDNA to glutathione S-transferase (GST) cDNA and purified the res
ulting GST fusion protein. When,ve tested the fusion protein with unmodifie
d or cisplatin-modified oligonucleotides, we found that GST-YB-I bound more
strongly to cisplatin-modified oligonucleotides, as did GST fusion protein
s of high mobility group 1 (HMG1), HMG2, and xeroderma pigmentosum group A
protein. When we assayed the ability of proliferating cell nuclear antigen
(PCNA) to interact with the GST fusion proteins, we observed binding to YB-
1 but not to HMG1, HMG2, or xeroderma pigmentosum group A. Subsequent exper
iments demonstrated that YB-1 and PCNA interact directly via the COOH-termi
nal region of YB-I. Using immunochemical coprecipitation methods, we observ
ed binding of YB-l and PCNA in vivo. These results suggest that YB-1 can fu
nction as a recognition protein for cisplatin-damaged DNA and that it may b
e important in DNA repair or in directing the cellular response to DNA dama
ge.