Identification of nuclear pre-replication centers poised for DNA synthesis in Xenopus egg extracts: immunolocalization study of replication protein A - PubMed (original) (raw)

Identification of nuclear pre-replication centers poised for DNA synthesis in Xenopus egg extracts: immunolocalization study of replication protein A

Y Adachi et al. J Cell Biol. 1992 Oct.

Abstract

We demonstrate by immunofluorescence that a 70-kD protein (P70) purified from Xenopus egg extracts is associated with subnuclear foci (about 200) which we propose to be an assembly of DNA pre-replication centers (preRCs). A cDNA encoding this protein reveals that P70 is the Xenopus homologue of replication protein A (RPA also called RF-A). RPA is know to be a cellular, three-subunit single-stranded DNA binding protein, which assists T-antigen in the assembly of the pre-priming complex in the SV40 replication system. The punctated preRCs exist transiently; they form post-mitotically during the period of nuclear membrane breakdown and disappear during ongoing DNA replication. P70 is homogeneously associated with chromatin at the later stages of the S-phase and is displaced from chromatin post replication, so that P70 cannot be detected on mitotic chromosomes. Double-immunofluorescence studies using biotin-dUTP demonstrate that initiation of DNA synthesis is confined to preRCs, resulting in the punctated replication pattern observed previously by others. PreRCs form efficiently on decondensed chromatin in membrane-free egg extracts if ATP and divalent cations are present. Our results suggest that preRCs are composed of an assembly of a large number of pre-initiation replication complexes poised for initiation at discreet subnuclear regions prior to nuclear reconstruction and initiation of DNA synthesis.

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References

    1. EMBO J. 1986 Mar;5(3):501-10 - PubMed
    1. EMBO J. 1986 Jun;5(6):1403-10 - PubMed
    1. J Cell Biol. 1985 Aug;101(2):518-23 - PubMed
    1. Nature. 1970 Aug 15;227(5259):680-5 - PubMed
    1. Proc Natl Acad Sci U S A. 1984 Nov;81(22):6973-7 - PubMed

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