MAMMALIAN UBIQUITIN-CONJUGATING ENZYME UBC9 INTERACTS WITH RAD51 RECOMBINATION PROTEIN AND LOCALIZES IN SYNAPTONEMAL COMPLEXES

Hsubc9, a human gene encoding a ubiquitin-conjugating enzyme, has been cloned. The 18-kDa HsUbc9 protein is homologous to the ubiquitin-conj ugating enzymes Hus5 of Schizosaccharomyces pombe and Ubc9 of Saccharo myces cerevisiae, The Hsubc9 gene complements a ubc9 mutation of S. ce revisiae. It has been mapped to chromosome 16p13.3 and is expressed in many human tissues, with the highest levels in testis and thymus, Acc ording to the Ga14 two-hybrid system analysis, HsUbc9 protein interact s with human recombination protein Rad51, A mouse homolog, Mmubc9, enc odes an amino acid sequence that is identical to the human protein, In mouse spermatocytes, MmUbc9 protein, like Rad51 protein, localizes in synaptonemal complexes, which suggests that Ubc9 protein plays a regu latory role in meiosis.