THE INFLUENCE OF THE PROLIFERATING CELL NUCLEAR ANTIGEN-INTERACTING DOMAIN OF P21(CIP1) ON DNA-SYNTHESIS CATALYZED BY THE HUMAN AND SACCHAROMYCES-CEREVISIAE POLYMERASE-DELTA HOLOENZYMES

In eukaryotes, processive DNA synthesis catalyzed by DNA polymerases d elta and epsilon (pol delta and epsilon) requires the proliferating ce ll nuclear antigen (PCNA). It has recently been shown that in humans ( h), the PCNA function, required for both DNA replication and nucleotid e excision repair, can be inactivated by p21(CIP1) due to a specific i nteraction between hPCNA and the carboxyl terminus of p21(CIP1). I,thi s report, we show that Saccharomyces cerevisiae (S. cerevisiae) PCNA-d ependent pol delta-catalyzed DNA synthesis was inhibited less efficien tly than the human system by the intact p21(CIP1) protein and was unaf fected by the p21(CIP1) carboxyl-terminal peptide (codons 139-160). Th is species-specific response of PCNA to p21(CIP1)-mediated inhibition of DNA synthesis results from a marked difference in the ability of h and S. cerevisiae PCNA to interact with p21(CIP1). AS shown by binding studies using the surface plasmon resonance technique, hPCNA hinds bo th full-length p21(CIP1) and the p21(CIP1) peptide-(139-160) stoichiom etrically with a similar affinity (K-D similar to 2.5 nM) while S. cer evisiae PCNA binds p21(CIP1) with similar to 10-fold less affinity and does not interact with the p21(CIP1) peptide-(139-160).