A Role for SUMO in meiotic chromosome synapsis.
During meiotic prophase, homologous chromosomes engage in a complex series of interactions that ensure their proper segregation at meiosis I. A central player in these interactions is the synaptonemal complex (SC), a proteinaceous structure elaborated along the lengths of paired homologs. In mutants that fail to make SC, crossing over is decreased, and chromosomes frequently fail to recombine; consequently, many meiotic products are inviable because of aneuploidy. Here, we have investigated the role of the small ubiquitin-like protein modifier (SUMO) in SC formation during meiosis in budding yeast. We show that SUMO localizes specifically to synapsed regions of meiotic chromosomes and that this localization depends on Zip1, a major building block of the SC. A non-null allele of the UBC9 gene, which encodes the SUMO-conjugating enzyme, impairs Zip1 polymerization along chromosomes. The Ubc9 protein localizes to meiotic chromosomes, coincident with SUMO staining. In the zip1 mutant, SUMO localizes to discrete foci on chromosomes. These foci coincide with axial associations, where proteins involved in synapsis initiation are located. Our data suggest a model in which SUMO modification of chromosomal proteins promotes polymerization of Zip1 along chromosomes. The ubc9 mutant phenotype provides the first evidence for a cause-and-effect relationship between sumoylation and synapsis.
Hooker
Gillian W
GW
Department of Molecular, Cellular, and Developmental Biology, Yale University, 266 Whitney Avenue, New Haven, Connecticut 06511, USA.
Roeder
G Shirleen
GS
D023902:Chromosome Pairing / Q000502:physiology*; D015825:Chromosomes, Fungal / Q000378:metabolism / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008540:Meiosis / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D004718:Saccharomycetales / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013573:Synaptonemal Complex / Q000378:metabolism
D005656:Fungal Proteins; D012097:Repressor Proteins; C099362:SMT3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025841:Small Ubiquitin-Related Modifier Proteins