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Cell cycle regulated phosphorylation of RPA‐32 occurs within the replication initiation complex.
Author(s) -
Fotedar R.,
Roberts J.M.
Publication year - 1992
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1992.tb05277.x
Subject(s) - dna replication , biology , cell cycle , origin recognition complex , dna , eukaryotic dna replication , cell division , protein subunit , associate editor , microbiology and biotechnology , cancer , genetics , cell , library science , gene , computer science
The transition from G1 to S phase of the cell cycle may be regulated by modification of proteins which are essential for initiating DNA replication. One of the first events during initiation is to unwind the origin DNA and this requires a single‐stranded DNA binding protein. RPA, a highly conserved multi‐subunit single‐stranded DNA binding protein, was first identified as a cellular protein necessary for the initiation of SV40 DNA replication. The 32 kDa subunit of RPA has been shown to be phosphorylated at the start of S phase. Using SV40 replication as a model, we have reproduced in vitro the S phase‐dependent phosphorylation of RPA‐32 and show that it occurs specifically within the replication initiation complex. Phosphorylated RPA‐32 is predominantly associated with DNA. Phosphorylation is not a pre‐requisite for association with DNA, but occurs after RPA binds to single‐stranded DNA formed at the origin during the initiation phase. The protein kinase(s) which phosphorylates RPA‐32 is present at all stages of the cell cycle but RPA‐32 does not bind to the SV40 origin or become phosphorylated in extracts from G1 cells. Therefore, the cell cycle‐dependent phosphorylation of RPA‐32 may be regulated by its binding to single‐stranded origin DNA during replication initiation.