Role of Ndt80, Sum1, and Swe1 as targets of the meiotic recombination checkpoint that control exit from pachytene and spore formation in Saccharomyces cerevisiae

Mol Cell Biol. 2002 Sep;22(18):6430-40. doi: 10.1128/MCB.22.18.6430-6440.2002.

Abstract

The meiotic recombination checkpoint, which is triggered by defects in recombination or chromosome synapsis, arrests sporulating cells of Saccharomyces cerevisiae at pachytene by preventing accumulation of active Clb-Cdc28. We compared the effects of manipulating the three known targets of the meiotic recombination checkpoint, NDT80, SWE1, and SUM1, in dmc1-arrested cells. Ndt80 is an activator of a set of middle sporulation-specific genes (MSGs), which includes CLB genes and genes involved in spore wall formation; Swe1 inhibits Clb-Cdc28 activity; and Sum1 is a repressor of NDT80 and some MSGs. Activation of the checkpoint leads to inhibition of Ndt80 activity and to stabilization of Swe1 and Sum1. Thus, dmc1-arrested cells fail to express MSGs, arrest at pachytene, and do not form spores. Our study shows that dmc1/dmc1 sum1/sum1 cells expressed MSGs prematurely and at high levels, entered the meiotic divisions efficiently, and in some cases formed asci containing mature spores. In contrast, dmc1/dmc1 swe1/swe1 cells expressed MSGs at a very low level, were inefficient and delayed in entry into the meiotic divisions, and never formed mature spores. We found that cells of dmc1/dmc1 sum1/sum1 ndt80/ndt80 and dmc1/dmc1 swe1/swe1 ndt80/ndt80 strains arrested at pachytene and that dmc1/dmc1 or dmc1/dmc1 swe1/swe1 cells overexpressing NDT80 were less efficient in bypassing checkpoint-mediated arrest than dmc1/dmc1 sum1/sum1 cells. Our results are consistent with previous suggestions that increased Clb-Cdc28 activity, caused by mutation of SWE1 or by an NDT80-dependent increase in CLB expression, allows dmc1/dmc1 cells to exit pachytene and that subsequent upregulation of Ndt80 activity by a feedback mechanism promotes entry into the meiotic divisions. Spore morphogenesis, however, requires efficient and timely activation of MSGs, which we speculate was achieved in dmc1/dmc1 sum1/sum1 cells by premature expression of NDT80.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Northern
  • Cell Cycle Proteins
  • DNA-Binding Proteins*
  • Fungal Proteins / physiology*
  • Gene Deletion
  • Genotype
  • Meiosis*
  • Models, Genetic
  • Mutation
  • Nuclear Proteins / physiology*
  • Plasmids / metabolism
  • Ploidies
  • Protein-Tyrosine Kinases / physiology*
  • Recombination, Genetic*
  • Repressor Proteins
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins*
  • Spores, Fungal / physiology*
  • Time Factors
  • Transcription Factors*

Substances

  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Fungal Proteins
  • NDT80 protein, S cerevisiae
  • Nuclear Proteins
  • Repressor Proteins
  • SUM1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • SWE1 protein, S cerevisiae
  • Protein-Tyrosine Kinases