MIS6, A FISSION YEAST INNER CENTROMERE PROTEIN, ACTS DURING G1 S AND FORMS SPECIALIZED CHROMATIN REQUIRED FOR EQUAL SEGREGATION/

Disorder in sister chromatid separation can lead to genome instability and cancer. A temperature-sensitive S. pombe mis6-302 frequently lose s a minichromosome at 26 degrees C and abolishes equal segregation of regular chromosomes at 36 degrees C. The mis6(+) gene is essential for viability, and its deletion results in missegregation identical to mi s6-302. Miss acts before or at the onset of S phase, and mitotic misse gregation defects are produced only after the passage of G1/S at 36 de grees C. Mise locates at the centromeres throughout the cell cycle. In the mutant, positioning of the centromeres becomes abnormal, and spec ialized chromatin in the inner centromeres, which give the smear micro coccal nuclease pattern in wild type, is disrupted. The ability to est ablish correct biorientation of sister centromeres in metaphase cells requires the Mis6-containing chromatin and originates during the passa ge of G1/S.