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J Cell Biol December 1, 1993; 123 (6 Pt 1): 1321-31.

Determination of initiation of DNA replication before and after nuclear formation in Xenopus egg cell free extracts.

Kubota Y , Takisawa H .

Xenopus egg extracts prepared before and after egg activation retain M- and S-phase specific activity, respectively. Staurosporine, a potent inhibitor of protein kinase, converted M-phase extracts into interphase-like extracts that were capable of forming nuclei upon the addition of sperm DNA. The nuclei formed in the staurosporine treated M-phase extract were incapable of replicating DNA, and they were unable to initiate replication upon the addition of S-phase extracts. Furthermore, replication was inhibited when the staurosporine-treated M-phase extract was added in excess to the staurosporine-treated S-phase extract before the addition of DNA. The membrane-depleted S-phase extract supported neither nuclear formation nor replication; however, preincubation of sperm DNA with these extracts allowed them to form replication-competent nuclei upon the addition of excess staurosporine-treated M-phase extract. These results demonstrate that positive factors in the S-phase extracts determined the initiation of DNA replication before nuclear formation, although these factors were unable to initiate replication after nuclear formation.

PubMed ID: 8253833
PMC ID: PMC2290898
Article link:

References [+] :
Adachi, Identification of nuclear pre-replication centers poised for DNA synthesis in Xenopus egg extracts: immunolocalization study of replication protein A. 1992, Pubmed, Xenbase