Asf1 Background Information CIA, an interactor of the CCG1 histone acetyltransferase subunit of TFIID, is a human histone chaperone. The Saccharomyces cerevisiae orthologue Asf1 (anti-silencing function 1) is involved in DNA repair response. Asf1, when overexpressed, causes de-repression of silent loci. Asf1 (also known as Asf1p) interacts with Bdf1p (bromodomain factor 1), which serves as the missing bromodomain in yTAF(II)145. Cell death in S. cerevisiae occurs with a phenotype that largely resembles apoptosis in multicellular organisms, but also has some features of passive cell death (necrosis). Deletion of Asf1 inhibits the normal assembly/disassembly of nucleosomes in yeast and thereby initiates the active cell death system. Yeast CAF-I and Asf1 cooperate to form nucleosomes in vitro . In vivo, Asf1 and Hir proteins physically interact and together promote heterochromatic gene silencing in a manner requiring PCNA. Chromatin assembly factor I mutants defective for PCNA binding require Asf1/Hir proteins for silencing.
