The DNA polymerase activity of Pol epsilon holoenzyme is required for rapid and efficient chromosomal DNA replication in Xenopus egg extracts.
BACKGROUND
DNA polymerase epsilon (Pol epsilon) is involved in DNA replication, repair, and cell-cycle checkpoint control in eukaryotic cells. Although the roles of replicative Pol alpha and Pol delta in chromosomal DNA replication are relatively well understood and well documented, the precise role of Pol epsilon in chromosomal DNA replication is not well understood.


RESULTS
This study uses a Xenopus egg extract DNA replication system to further elucidate the replicative role(s) played by Pol epsilon. Previous studies show that the initiation timing and elongation of chromosomal DNA replication are markedly impaired in Pol epsilon-depleted Xenopus egg extracts, with reduced accumulation of replicative intermediates and products. This study shows that normal replication is restored by addition of Pol epsilon holoenzyme to Pol epsilon-depleted extracts, but not by addition of polymerase-deficient forms of Pol epsilon, including polymerase point or deletion mutants or incomplete enzyme complexes. Evidence is also provided that Pol epsilon holoenzyme interacts directly with GINS, Cdc45p and Cut5p, each of which plays an important role in initiation of chromosomal DNA replication in eukaryotic cells.


CONCLUSIONS
These results indicate that the DNA polymerase activity of Pol epsilon holoenzyme plays an essential role in normal chromosomal DNA replication in Xenopus egg extracts. These are the first biochemical data to show the DNA polymerase activity of Pol epsilon holoenzyme is essential for chromosomal DNA replication in higher eukaryotes, unlike in yeasts.
Shikata
Koh
K
Laboratories for Biomolecular Networks, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan. shikata@tainetsu.com
Sasa-Masuda
Taro
T
Okuno
Yukiko
Y
Waga
Shou
S
Sugino
Akio
A
D000818:Animals; D002875:Chromosomes / Q000235:genetics*; D003001:Cloning, Molecular; D004257:DNA Polymerase II / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D005260:Female; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic; D009865:Oocytes / Q000502:physiology*; D016366:Open Reading Frames; D011994:Recombinant Proteins / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis
D011994:Recombinant Proteins; D029867:Xenopus Proteins; D004257:DNA Polymerase II