Nonrandom Homolog Segregation at Meiosis I in Schizosaccharomyces pombe Mutants Lacking Recombination

Corresponding author: Gerald R. Smith, 1100 Fairview Ave. North, A1-162, P.O. Box 19024, Seattle, WA 98109-1024., gsmith{at}fhcrc.org (E-mail)

Communicating editor: M. LICHTEN

Physical connection between homologous chromosomes is normally required for their proper segregation to opposite poles at the first meiotic division (MI). This connection is generally provided by the combination of reciprocal recombination and sister-chromatid cohesion. In the absence of meiotic recombination, homologs are predicted to segregate randomly at MI. Here we demonstrate that in rec12 mutants of the fission yeast Schizosaccharomyces pombe, which are devoid of meiosis-induced recombination, homologs segregate to opposite poles at MI 63% of the time. Residual, Rec12-independent recombination appears insufficient to account for the observed nonrandom homolog segregation. Dyad asci are frequently produced by rec12 mutants. More than half of these dyad asci contain two viable homozygous-diploid spores, the products of a single reductional division. This set of phenotypes is shared by other S. pombe mutants that lack meiotic recombination, suggesting that nonrandom MI segregation and dyad formation are a general feature of meiosis in the absence of recombination and are not peculiar to rec12 mutants. Rec8, a meiosis-specific sister-chromatid cohesin, is required for the segregation phenotypes displayed by rec12 mutants. We propose that S. pombe possesses a system independent of recombination that promotes homolog segregation and discuss possible mechanisms.

This article has been cited by other articles:

				G. A. Cromie, R. W. Hyppa, and G. R. Smith The Fission Yeast BLM Homolog Rqh1 Promotes Meiotic Recombination Genetics, July 1, 2008; 179(3): 1157 - 1167. [Abstract] [Full Text] [PDF]

				G. Octobre, A. Lorenz, J. Loidl, and J. Kohli The Rad52 Homologs Rad22 and Rti1 of Schizosaccharomyces pombe Are Not Essential for Meiotic Interhomolog Recombination, but Are Required for Meiotic Intrachromosomal Recombination and Mating-Type-Related DNA Repair Genetics, April 1, 2008; 178(4): 2399 - 2412. [Abstract] [Full Text] [PDF]

				S. E. Thomas and B. D. McKee Meiotic Pairing and Disjunction of Mini-X Chromosomes in Drosophila Is Mediated by 240-bp rDNA Repeats and the Homolog Conjunction Proteins SNM and MNM Genetics, October 1, 2007; 177(2): 785 - 799. [Abstract] [Full Text] [PDF]

				M. Pradillo, E. Lopez, C. Romero, E. Sanchez-Moran, N. Cunado, and J. L. Santos An Analysis of Univalent Segregation in Meiotic Mutants of Arabidopsis thaliana: A Possible Role for Synaptonemal Complex Genetics, February 1, 2007; 175(2): 505 - 511. [Abstract] [Full Text] [PDF]

				L. Davis and G. R. Smith The Meiotic Bouquet Promotes Homolog Interactions and Restricts Ectopic Recombination in Schizosaccharomyces pombe Genetics, September 1, 2006; 174(1): 167 - 177. [Abstract] [Full Text] [PDF]

				K. Ogino, K. Hirota, S. Matsumoto, T. Takeda, K. Ohta, K.-i. Arai, and H. Masai Hsk1 kinase is required for induction of meiotic dsDNA breaks without involving checkpoint kinases in fission yeast PNAS, May 23, 2006; 103(21): 8131 - 8136. [Abstract] [Full Text] [PDF]

				J. A. Farah, G. Cromie, L. Davis, W. W. Steiner, and G. R. Smith Activation of an Alternative, Rec12 (Spo11)-Independent Pathway of Fission Yeast Meiotic Recombination in the Absence of a DNA Flap Endonuclease Genetics, December 1, 2005; 171(4): 1499 - 1511. [Abstract] [Full Text] [PDF]

				C. Ellermeier and G. R. Smith Cohesins are required for meiotic DNA breakage and recombination in Schizosaccharomyces pombe PNAS, August 2, 2005; 102(31): 10952 - 10957. [Abstract] [Full Text] [PDF]

				L. Davis and G. R. Smith Dynein Promotes Achiasmate Segregation in Schizosaccharomyces pombe Genetics, June 1, 2005; 170(2): 581 - 590. [Abstract] [Full Text] [PDF]

				J. A. Farah, G. Cromie, W. W. Steiner, and G. R. Smith A Novel Recombination Pathway Initiated by the Mre11/Rad50/Nbs1 Complex Eliminates Palindromes During Meiosis in Schizosaccharomyces pombe Genetics, March 1, 2005; 169(3): 1261 - 1274. [Abstract] [Full Text] [PDF]

				G. A. Cromie, C. A. Rubio, R. W. Hyppa, and G. R. Smith A Natural Meiotic DNA Break Site in Schizosaccharomyces pombe Is a Hotspot of Gene Conversion, Highly Associated With Crossing Over Genetics, February 1, 2005; 169(2): 595 - 605. [Abstract] [Full Text] [PDF]

				M. K. Davidson, N. P. Young, G. G. Glick, and W. P. Wahls Meiotic chromosome segregation mutants identified by insertional mutagenesis of fission yeast Schizosaccharomyces pombe; tandem-repeat, single-site integrations Nucleic Acids Res., August 17, 2004; 32(14): 4400 - 4410. [Abstract] [Full Text] [PDF]

				T. T. Saito, T. Tougan, T. Kasama, D. Okuzaki, and H. Nojima Mcp7, a meiosis-specific coiled-coil protein of fission yeast, associates with Meu13 and is required for meiotic recombination Nucleic Acids Res., June 21, 2004; 32(11): 3325 - 3339. [Abstract] [Full Text] [PDF]

				J. A. Young, R. W. Hyppa, and G. R. Smith Conserved and Nonconserved Proteins for Meiotic DNA Breakage and Repair in Yeasts Genetics, June 1, 2004; 167(2): 593 - 605. [Abstract] [Full Text] [PDF]

				A. L. Grishchuk and J. Kohli Five RecA-like Proteins of Schizosaccharomyces pombe Are Involved in Meiotic Recombination Genetics, November 1, 2003; 165(3): 1031 - 1043. [Abstract] [Full Text] [PDF]