Zinc Finger Associated Domain of Drosophila melanogaster, its Evolution and Phylogenetic RestrictionThe

Abstract

The Drosophila melanogaster genome contains 359 C2H2 zinc finger protein (ZFP) coding During an in-depth analysis of these proteins I identified a sequence motif that can be found at the N-terminus of 94 ZFP coding genes (26.1%). It has been named zinc finger associated domain (ZAD), since it is almost exclusively asociated with C2H2 zinc finger motifs, with the exception of four genes that code for proteins with isolated ZADs. The ZAD represents an independently folding domain that is stabilised by zinc coordination. It mediates homodimer formation and probably association of closely related ZAD family members. The ZAD coding genes fall into two large subsets: subset 1 where the ZAD is encoded by a single exon and subset 2 where the ZAD is coded by two exons. I propose that subset 1 ZADs have lost their intron at multiple time points by distinct retroposition events. The majority of ZAD coding genes in Drosophila melanogaster were generated by local gene duplication events, which is consistent with the observation that the ZAD coding genes participates in lineage-specific expansions in three fly species. The finding that many ZAD coding genes are specific for a given species prompted the idea that these genes may be involved in mechanisms that maintain genetic divergence during speciation. My results show that ZAD coding genes are overrepresented in a class of genes that represent putative speciation genes.