ORIGINAL PAPER

Molecular and General Genetics MGG

, Volume 253, Issue 3, pp 278-288

A meiosis-specific protein kinase, Ime2, is required for the correct timing of DNA replication and for spore formation in yeast meiosis

  • M. FoianiAffiliated withDipartimento di Genetica e di Biologia dei Microrganismi, Universita’ degli Studi di Milano, I-20133 Milan, Italy
  • , E. Nadjar-BogerAffiliated withFaculty of Biology, Technion, Haifa, 32000 Israel
  • , R. CaponeAffiliated withDipartimento di Genetica e di Biologia dei Microrganismi, Universita’ degli Studi di Milano, I-20133 Milan, Italy
  • , S. SageeAffiliated withFaculty of Biology, Technion, Haifa, 32000 Israel
  • , T. HashimshoniAffiliated withFaculty of Biology, Technion, Haifa, 32000 Israel
  • , Y. KassirAffiliated withFaculty of Biology, Technion, Haifa, 32000 Israel

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Abstract

 In this report we study the regulation of premeiotic DNA synthesis in Saccharomyces cerevisiae. DNA replication was monitored by fluorescence-activated cell sorting analysis and by analyzing the pattern of expression of the DNA polymerase α-primase complex. Wild-type cells and cells lacking one of the two principal regulators of meiosis, Ime1 and Ime2, were compared. We show that premeiotic DNA synthesis does not occur in ime1Δ diploids, but does occur in ime2Δ diploids with an 8–9 h delay. At late meiotic times, ime2Δ diploids exhibit an additional round of DNA synthesis. Furthermore, we show that in wild-type cells the B-subunit of DNA polymerase α is phosphorylated during premeiotic DNA synthesis, a phenomenon that has previously been reported for the mitotic cell cycle. Moreover, the catalytic subunit and the B-subunit of DNA polymerase α are specifically degraded during spore formation. Phosphorylation of the B-subunit does not occur in ime1Δ diploids, but does occur in ime2Δ diploids with an 8–9 h delay. In addition, we show that Ime2 is not absolutely required for commitment to meiotic recombination, spindle formation and nuclear division, although it is required for spore formation.

Key words DNA replication Meiosis Saccharomyces cerevisiae