RNAi and heterochromatin repress centromeric meiotic recombination.
During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes, is essential in most species for proper homologue segregation. Nevertheless, recombination is repressed specifically in and around the centromeres of chromosomes, apparently because rare centromeric (or pericentromeric) recombination events, when they do occur, can disrupt proper segregation and lead to genetic disabilities, including birth defects. The basis by which centromeric meiotic recombination is repressed has been largely unknown. We report here that, in fission yeast, RNAi functions and Clr4-Rik1 (histone H3 lysine 9 methyltransferase) are required for repression of centromeric recombination. Surprisingly, one mutant derepressed for recombination in the heterochromatic mating-type region during meiosis and several mutants derepressed for centromeric gene expression during mitotic growth are not derepressed for centromeric recombination during meiosis. These results reveal a complex relation between types of repression by heterochromatin. Our results also reveal a previously undemonstrated role for RNAi and heterochromatin in the repression of meiotic centromeric recombination and, potentially, in the prevention of birth defects by maintenance of proper chromosome segregation during meiosis.
Ellermeier
Chad
C
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA.
Higuchi
Emily C
EC
Phadnis
Naina
N
Holm
Laerke
L
Geelhood
Jennifer L
JL
Thon
Genevieve
G
Smith
Gerald R
GR
D002503:Centromere / Q000235:genetics*; D002868:Chromosomal Proteins, Non-Histone / Q000172:deficiency / Q000378:metabolism; D015825:Chromosomes, Fungal / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D006570:Heterochromatin / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008540:Meiosis / Q000235:genetics*; D008780:Methyltransferases / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D034622:RNA Interference; D011995:Recombination, Genetic; D012097:Repressor Proteins / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000166:cytology* / Q000201:enzymology / Q000235:genetics; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism; D014158:Transcription, Genetic
D002868:Chromosomal Proteins, Non-Histone; D006570:Heterochromatin; D006657:Histones; D012097:Repressor Proteins; D029702:Schizosaccharomyces pombe Proteins; C465958:Swi6 protein, S pombe; D008780:Methyltransferases; D008239:Lysine