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Synaptonemal Complex Central Region Proteins Promote Localization of Pro-crossover Factors to Recombination Events During Caenorhabditis elegans Meiosis.

Authors
  • Cahoon, Cori K1
  • Helm, Jacquellyn M1
  • Libuda, Diana E2
  • 1 Department of Biology, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403.
  • 2 Department of Biology, Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403 [email protected]
Type
Published Article
Journal
Genetics
Publisher
The Genetics Society of America
Publication Date
Oct 01, 2019
Volume
213
Issue
2
Pages
395–409
Identifiers
DOI: 10.1534/genetics.119.302625
PMID: 31431470
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Crossovers (COs) between homologous chromosomes are critical for meiotic chromosome segregation and form in the context of the synaptonemal complex (SC), a meiosis-specific structure that assembles between aligned homologs. During Caenorhabditis elegans meiosis, central region components of the SC (SYP proteins) are essential to repair double-strand DNA breaks (DSBs) as COs. Here, we investigate the relationships between the SYP proteins and conserved pro-CO factors by examining the immunolocalization of these proteins in meiotic mutants where SYP proteins are absent, reduced, or mislocalized. Although COs do not form in syp null mutants, pro-CO factors COSA-1, MSH-5, and ZHP-3 nevertheless colocalize at DSB-dependent sites during late prophase, reflecting an inherent affinity of these factors for DSB repair sites. In contrast, in mutants where SYP proteins are present but form aggregates or display abnormal synapsis, pro-CO factors consistently track with SYP-1 localization. Further, pro-CO factors usually localize to a single site per SYP-1 structure, even in SYP aggregates or in mutants where the SC forms between sister chromatids, suggesting that CO regulation occurs within these aberrant SC structures. Moreover, we find that the meiotic cohesin REC-8 is required to ensure that SC formation occurs between homologs and not sister chromatids. Taken together, our findings support a model in which SYP proteins promote CO formation by promoting the localization of pro-CO factors to recombination events within an SC compartment, thereby ensuring that pro-CO factors identify a recombination event within an SC structure and that CO maturation occurs only between properly aligned homologous chromosomes. Copyright © 2019 by the Genetics Society of America.

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