RCC1, a regulator of mitosis, is essential for DNA replication.
Temperature-sensitive mutants in the RCC1 gene of BHK cells fail to maintain a correct temporal order of the cell cycle and will prematurely condense their chromosomes and enter mitosis at the restrictive temperature without having completed S phase. We have used Xenopus egg extracts to investigate the role that RCC1 plays in interphase nuclear functions and how this role might contribute to the known phenotype of temperature-sensitive RCC1 mutants. By immunodepleting RCC1 protein from egg extracts, we find that it is required for neither chromatin decondensation nor nuclear formation but that it is absolutely required for the replication of added sperm chromatin DNA. Our results further suggest that RCC1 does not participate enzymatically in replication but may be part of a structural complex which is required for the formation or maintenance of the replication machinery. By disrupting the replication complex, the loss of RCC1 might lead directly to disruption of the regulatory system which prevents the initiation of mitosis before the completion of DNA replication.
Dasso
M
M
Department of Biology B-022, University of California, San Diego, La Jolla 92037.
Nishitani
H
H
Kornbluth
S
S
Nishimoto
T
T
Newport
J W
JW
D000818:Animals; D018797:Cell Cycle Proteins; D002460:Cell Line; D002843:Chromatin / Q000502:physiology*; D006224:Cricetinae; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005809:Genes, Regulator; D020662:Guanine Nucleotide Exchange Factors; D007700:Kinetics; D008938:Mitosis / Q000235:genetics*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D009707:Nucleosomes / Q000502:physiology; D009865:Oocytes / Q000502:physiology; D010957:Plasmids; D011994:Recombinant Proteins / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D009707:Nucleosomes; C499304:RCC1 protein, Xenopus; D011994:Recombinant Proteins; D029867:Xenopus Proteins