A murine replication protein accumulates temporarily in the heterochromatic regions of nuclei prior to initiation of DNA replication.
We have analyzed the expression of the murine P1 gene, the mammalian homologue of the yeast MCM3 protein, during the mitotic cell cycle. The MCM3 protein has previously been shown to be of importance for initiation of DNA replication in Saccharomyces cerevisiae. We found that the murine P1 protein was present in the nuclei of mammalian cells throughout interphase of the cell cycle. This is in contrast to the MCM3 protein, which is located in the nuclei of yeast cells only between the M and the S phase of the cell cycle. Detailed analysis of the intranuclear localization of the P1 protein during the cell cycle revealed that it accumulates transiently in the heterochromatic regions towards the end of G1. The accumulation of the P1 protein in the heterochromatic regions prior to activation of DNA replication suggests that the mammalian P1 protein is also of importance for initiation of DNA replication. The MCM2-3.5 proteins have been suggested to represent yeast equivalents of a hypothetical replication licensing factor initially described in Xenopus. Our data support this model and indicate that the murine P1 protein could function as replication licensing factor. The chromosomal localization of the P1 gene was determined by fluorescence in situ hybridization to region 6p12 in human metaphase chromosomes.
Starborg
M
M
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institute, Stockholm, Sweden.
Brundell
E
E
Gell
K
K
Larsson
C
C
White
I
I
Daneholt
B
B
Höög
C
C
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002874:Chromosome Mapping; D002896:Chromosomes, Human, Pair 6; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D004261:DNA Replication; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins; D006570:Heterochromatin / Q000378:metabolism*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D051379:Mice; D064126:Minichromosome Maintenance Complex Component 3; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins
D018797:Cell Cycle Proteins; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D006570:Heterochromatin; C066470:MCM3 protein, human; C069200:MCM5 protein, S cerevisiae; C489423:MCM5 protein, human; C513269:Mcm3 protein, mouse; C489424:Mcm5 protein, mouse; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D029867:Xenopus Proteins; C489425:mcm5 protein, Xenopus; D064126:Minichromosome Maintenance Complex Component 3