CHARACTERIZATION OF THE CP COMPLEX, AN ABUNDANT DIMER OF CDC68 AND POB3 PROTEINS THAT REGULATES YEAST TRANSCRIPTIONAL ACTIVATION AND CHROMATIN REPRESSION

The Cdc68 protein of the yeast Saccharomyces cerevisiae is an essentia l nuclear protein that has been shown to be necessary for the tl-ans-a ctivation of many genes as well as for the maintenance of chromatin-me diated repression in the absence of trans-activation, These activities implicate, the Cdc68 protein in the regulation of chromatin structure and/or function, Here we report that Cdc68 is found in association wi th another essential nuclear protein, Pob3, in what we term the CP com plex. This dimer of Cdc68 with Pob3 is stable to partial purification, so that the functions of gene activation and repression that are assi gned to Cdc68 are likely to be properties of the CP complex. The CP co mplex is highly abundant, suggesting that it may be widespread through out chromatin.