PCG COMPLEXES AND CHROMATIN SILENCING

Silencing complexes in yeast and in the fly have many similarities. Th is repressive complex is assembled by a chain of recruitment; its exte nt and stability depend on the concentration of components and affect an extended chromatin region, probably through interactions with nucle osomes. Recent results show that assembly of the complex is antagonize d by transcriptional activity in the region but is favored by interact ions with other complexes nearby or in other regions that associate in the same nuclear environment. How such a complex interferes with tran scriptional activity is not entirely clear but current evidence sugges ts that they compete with the chromatin structure required for the bin ding of activators.