CLONING OF DROSOPHILA GCN5 - CONSERVED FEATURES AMONG METAZOAN GCN5 FAMILY MEMBERS

PCAF and hGCN5 are distinct human genes that encode proteins related t o the yeast histone acetyltransferase and transcriptional adapter GCN5 . The PCAF protein shares extensive similarity with the 439 amino acid s of yGCN5, hut it has an similar to 350 amino acid N-terminal extensi on that interacts with the transcriptional co-activator p300/CBP. Aden oviral protein E1a can disrupt PCAF-CBP interactions and prevent PCAF- dependent cellular differentiation. In this report, we describe the cl oning and initial characterization of a Drosophila homolog of yGCN5. I n addition to the homology to yGCN5, the Drosophila protein shares seq uence similarity with the N-terminal portion of human PCAF that is inv olved in binding to CBP. In the course of characterizing dGCN5, we hav e discovered that hGCN5 also contains an N-terminal extension with sig nificant similarity to PCAF. Interestingly, in the case of the hGCN5 g ene, alternative splicing may regulate the production of full-length h GCN5. The presence of the N-terminal domain in a Drosophila GCN5 homol og and both human homologs suggests that it was part of the ancestral form of metazoan GCN5.