The N-terminal noncatalytic region of Xenopus RecQ4 is required for chromatin binding of DNA polymerase alpha in the initiation of DNA replication.
Recruitment of DNA polymerases onto replication origins is a crucial step in the assembly of eukaryotic replication machinery. A previous study in budding yeast suggests that Dpb11 controls the recruitment of DNA polymerases alpha and epsilon onto the origins. Sld2 is an essential replication protein that interacts with Dpb11, but no metazoan homolog has yet been identified. We isolated Xenopus RecQ4 as a candidate Sld2 homolog. RecQ4 is a member of the metazoan RecQ helicase family, and its N-terminal region shows sequence similarity with Sld2. In Xenopus egg extracts, RecQ4 is essential for the initiation of DNA replication, in particular for chromatin binding of DNA polymerase alpha. An N-terminal fragment of RecQ4 devoid of the helicase domain could rescue the replication activity of RecQ4-depleted extracts, and antibody against the fragment inhibited DNA replication and chromatin binding of the polymerase. Further, N-terminal fragments of RecQ4 physically interacted with Cut5, a Xenopus homolog of Dpb11, and their ability to bind to Cut5 closely correlated with their ability to rescue the replication activity of the depleted extracts. Our data suggest that RecQ4 performs an essential role in the assembly of replication machinery through interaction with Cut5 in vertebrates.
Matsuno
Kumiko
K
Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.
Kumano
Maya
M
Kubota
Yumiko
Y
Hashimoto
Yoshitami
Y
Takisawa
Haruhiko
H
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004256:DNA Polymerase I / Q000378:metabolism*; D004261:DNA Replication; D004268:DNA-Binding Proteins; D008969:Molecular Sequence Data; D025941:Protein Interaction Mapping; D053484:RecQ Helicases; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics
D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; C509993:TopBP1 protein, Xenopus; D029867:Xenopus Proteins; D004256:DNA Polymerase I; D004265:DNA Helicases; D053484:RecQ Helicases