Cdc6 is an unstable protein whose de novo synthesis in G1 is important for the onset of S phase and for preventing a 'reductional' anaphase in the budding yeast Saccharomyces cerevisiae

Simonetta Piatti, Christoph Lengauer, Kim Nasmyth

Research output: Contribution to journalArticlepeer-review

Abstract

S phase entry depends on cyclin-dependent kinases whose activation during late G1 is due partly to the synthesis of unstable cyclin subunits. We identify here a second type of unstable protein, Cdc6, whose synthesis during G1 is important for initiation of DNA replication. The CDC6 gene is normally transcribed at the end of mitosis, but in cells with a prolonged G1 phase there is a second burst of transcription in late G1. The former is due to Swi5, while the latter is due to MBF or SBF transcription factors. Small G1 cells that cannot synthesize Cdc6 in late G1 progress through S phase very slowly. Cells that transcribe CDC6 neither at the end of mitosis nor in late G1 fail to replicate DNA but, despite this, undergo mitosis and produce daughter cells with fractional DNA contents. This 'reductional anaphase occurs with almost wild-type kinetics and depends on the activity of G2 cyclins. Thus, cells that fail to duplicate chromosomes due to a cdc6 defect cannot prevent the onset of mitosis, unlike other mutants with replication defects. We show, by fluorescence in situ hybridization, that chromosomes which remain unduplicated due to a lack of Cdc6 synthesis are segregated intact to spindle poles during the 'reductional anaphase.

Original languageEnglish (US)
Pages (from-to)3788-3799
Number of pages12
JournalThe EMBO journal
Volume14
Issue number15
StatePublished - 1995

Keywords

  • CDC6
  • Chromosome segregation
  • DNA replication
  • Mitosis
  • Transcriptional regulation

ASJC Scopus subject areas

  • Cell Biology
  • Genetics

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