THE COHESION PROTEIN MEI-S332 LOCALIZES TO CONDENSED MEIOTIC AND MITOTIC CENTROMERES UNTIL SISTER CHROMATIDS SEPARATE

The Drosophila MEI-S332 protein has been shown to be required for the maintenance of sister-chromatid cohesion in male and female meiosis. T he protein localizes to the centromeres during male meiosis when the s ister chromatids are attached, and it is no longer detectable after th ey separate. Drosophila melanogaster male meiosis is atypical in sever al respects, making it important to define MEI-S332 behavior during fe male meiosis, which better typifies meiosis in eukaryotes. We find tha t MEI-S332 localizes to the centromeres of prometaphase I chromosomes in oocytes, remaining there until it is delocalized at anaphase II. By using oocytes we were able to obtain sufficient material to investiga te the fate of MEI-S332 after the metaphase II-anaphase II transition. The levels of MEI-S332 protein are unchanged after the completion of meiosis, even when translation is blocked, suggesting that the protein dissociates from the centromeres but is not degraded at the onset of anaphase II. Unexpectedly, MEI-S332 is present during embryogenesis, l ocalizes onto the centromeres of mitotic chromosomes, and is delocaliz ed from anaphase chromosomes. Thus, MEI-S332 associates with the centr omeres of both meiotic and mitotic chromosomes and dissociates from th em at anaphase.