Vol. 46 (2004), N 1, p. 43-52

A STUDY OF DYNAMICS OF SOME POSTREPLICATION DNA REPAIR PROTEINS IN CARCINOGEN-DAMAGED MAMMALIAN CELLS A. A. Nikiforov,1 * M. P. Svetlova,1 L. V. Solovjeva,1 M. Ziegler,2 S. Oei,2 N. Nikolaishvili-Feinberg,3 M. Cordeiro-Stone,3 N. V. Tomilin1 1 'institute of Cytology RAS, St. Petersburg, Russia, 2 Institute of Biochemistry, Free University of Berlin, Germany, and 2 University of North Carolina at Chapel Hill, USA; * e-mail: nikiforovan@hotmail.com Many types of DNA lesions in template strands block DNA replication and lead to a stalling of replication forks. This block can be overcome (bypassed) by special DNA polymerases (for example, DNA polymerase η, Polη) that perform translesion synthesis on damaged template DNA. The phenomenon of completing DNA replication, while DNA lesions remain in the template strands, has been named post-replication repair (PRR). In yeast Saccharomyces cerevisiae, PRR includes mutagenic and error-free pathways under the regultion of the RAD6/RAD18 complex, which induces ubiquitylation of PCNA. In mammalian cells, Polη accumulates in replication foci but the mechanism of this accumulation is not known. Polη possesses a conserved PCNA binding motif at the C terminal and phosphorylation of this motif might be essential for its interaction with PCNA. We have shown previously that staurosporine, an inhibitor of protein kinases, inhibits PRR in human cells. In this study we examined whether the accumulation of Polη in replication foci after DNA damage is dependent on phosphorylation of the PCNA binding motif. We also studied DNA damage-induced phosphorylation of GFP-tagged human Rad18 (hRad18) and its accumulation in replication foci. Our data indicate that (1) Polη is not phosphorylated in response to UV irradiation or MMS treatment, but its diffusional mobility is slightly decreased, and (2) hRad18 accumulates in MMS-treated cells, and considerable amount of the protein co-localizes with detergent insoluble PCNA in replication foci; these responses are sensitive to staurosporine. Our data suggest that hRad18 phosphorylation is the staurosporine-sensitive PRR step. Key words:  post-replication DNA repair, DNA polymerase η, белок hRad18 Back    Contents    Main