DNA polymerase alpha associated protein P1, a murine homolog of yeast MCM3, changes its intranuclear distribution during the DNA synthetic period.
We isolated a murine gene for the DNA polymerase alpha associated protein P1, which shares high homology with the budding yeast MCM3 protein, which is a member of a protein family involved in the early event of DNA replication having a putative DNA-dependent ATPase motif. Using a polyclonal anti-P1 antibody raised against a beta-galactosidase-P1 fusion protein, we identified at least two forms of P1 protein in the nucleus of a mouse cell line, an underphosphorylated form that was associated with a particular nuclear structure and a hyperphosphorylated form loosely bound to the nucleus. During progression through S phase, P1 disappeared, first from the euchromatic region, then from the heterochromatic region, apparently in parallel with temporally ordered DNA replication. Thus, it is likely that the underphosphorylated P1 is dissociated from the nuclear structure after DNA replication by cell cycle-dependent phosphorylation. This is the first direct observation of a protein whose behavior is consistent with that of a hypothetical factor which restricts the chromatin to replicate once per cell cycle in higher eukaryotes.
Kimura
H
H
Research Center for Molecular Genetics, Faculty of Science, Hokkaido University, Sapporo, Japan.
Nozaki
N
N
Sugimoto
K
K
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D001483:Base Sequence; D002451:Cell Compartmentation; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D002458:Cell Fractionation; D002467:Cell Nucleus / Q000737:chemistry / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis* / Q000187:drug effects; D004257:DNA Polymerase II / Q000378:metabolism; D004268:DNA-Binding Proteins; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000235:genetics; D015151:Immunoblotting; D051379:Mice; D064126:Minichromosome Maintenance Complex Component 3; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D010766:Phosphorylation; D011233:Precipitin Tests; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors
D000906:Antibodies; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C513269:Mcm3 protein, mouse; D009687:Nuclear Proteins; D014157:Transcription Factors; D004247:DNA; D004257:DNA Polymerase II; D064126:Minichromosome Maintenance Complex Component 3