2 GENES REQUIRED FOR THE BINDING OF AN ESSENTIAL SACCHAROMYCES-CEREVISIAE KINETOCHORE COMPLEX TO DNA

Kinetochores are DNA-protein structures that assemble on centromeric D NA and attach chromosomes to spindle microtubules. Because of their si mplicity, the 125-bp centromeres of Saccharomyces cerevisiae are parti cularly amenable to molecular analysis, Budding yeast centromeres cont ain three sequence elements of which centromere DNA sequence element I n (CDEIII) appears to be particularly important, cis-acting mutations in CDEIII and trans-acting mutations in genes encoding subunits of the CDEIII-binding complex (CBF3) prevent correct chromosome transmission , Using temperature-sensitive mutations in CBF3 subunits, we show a st rong correlation between DNA-binding activity measured in vitro and ki netochore activity in vivo. We extend previous findings by Goh and Kil martin [Goh, P.-Y. & Kilmartin, J, V, (1993) J, Cell Biol, 121, 503-51 2] to argue that DNA-bound CBF3 may be involved in the operation of a mitotic checkpoint but that functional CBF3 is not required for the as sembly of a bipolar spindle.