mei-P22 encodes a chromosome-associated protein required for the initiation of meiotic recombination in Drosophila melanogaster.
Double-strand breaks (DSB) initiate meiotic recombination in a variety of organisms. Here we present genetic evidence that the mei-P22 gene is required for the induction of DSBs during meiotic prophase in Drosophila females. Strong mei-P22 mutations eliminate meiotic crossing over and suppress the sterility of DSB repair-defective mutants. Interestingly, crossing over in mei-P22 mutants can be restored to almost 50% of wild-type by X irradiation. In addition, an antibody-based assay was used to demonstrate that DSBs are not formed in mei-P22 mutants. This array of phenotypes is identical to that of mei-W68 mutants; mei-W68 encodes the Drosophila Spo11 homolog that is proposed to be an enzyme required for DSB formation. Consistent with a direct role in DSB formation, mei-P22 encodes a basic 35.7-kD protein, which, when examined by immunofluorescence, localizes to foci on meiotic chromosomes. MEI-P22 foci appear transiently in early meiotic prophase, which is when meiotic recombination is believed to initiate. By using an antibody to C(3)G as a marker for synaptonemal complex (SC) formation, we observed that SC is present before MEI-P22 associates with the chromosomes, thus providing direct evidence that the development of SC precedes the initiation of meiotic recombination. Similarly, we found that MEI-P22 foci did not appear in a c(3)G mutant in which SC does not form, suggesting that DSB formation is dependent on SC formation in Drosophila. We propose that MEI-P22 interacts with meiosis-specific chromosome proteins to facilitate DSB creation by MEI-W68.
Liu
Hao
H
Waksman Institute and Department of Genetics, Rutgers State University of New Jersey, Piscataway, New Jersey 08854-8020, USA.
Jang
Janet K
JK
Kato
Naohiro
N
McKim
Kim S
KS
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D004260:DNA Repair; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics; D008540:Meiosis; D008969:Molecular Sequence Data; D012313:RNA / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional; D011995:Recombination, Genetic
D012313:RNA