GINS Is a DNA polymerase ε accessory factor during chromosomal DNA replication in budding yeast

Abstract

GINS is a protein complex found in eukaryotic cells that is composed of Sld5p, Psf1p, Psf2p, and Psf3p. GINS polypeptides are highly conserved in eukaryotes, and the GINS complex is required for chromosomal DNA replication in yeasts and Xenopus egg. This study reports purification and biochemical characterization of GINS from Saccharomyces cerevisiae. The results presented here demonstrate that GINS forms a 1:1 complex with DNA polymerase ε (Pol ε) holoenzyme and greatly stimulates its catalytic activity in vitro. In the presence of GINS, Pol ε is more processive and dissociates more readily from replicated DNA, while under identical conditions, proliferating cell nuclear antigen slightly stimulates Pol ε in vitro. These results strongly suggest that GINS is a Pol ε accessory protein during chromosomal DNA replication in budding yeast. Based on these results, we propose a model for molecular dynamics at eukaryotic chromosomal replication fork. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.