MSL2 targets histone genes inDrosophila virilis

Abstract

AbstractHistone genes are amongst the most evolutionary conserved in eukaryotic genomes, yetcis-regulatory mechanisms of histone gene regulation differ considerably amongst species. InDrosophila melanogaster, an interaction between GA-richciselements in theH3/H4promoter and the GA-binding transcription factor CLAMP is important for promoting histone gene regulation and factor recruitment to the locus. CLAMP also participates in male dosage compensation by recruiting the Male Specific Lethal Complex (MSLc) to the X-chromosome. We discovered that the male-specific protein of MSLc, MSL2, is recruited to the autosomal major histone locus inD. virilisbut not to the minor locus or to the single histone locus in other species. While the histone coding sequences are well conserved between species, the critical GA-richciselements in theH3/H4promoter are poorly conserved betweenD. melanogasterandD. virilis. We show that CLAMP still targets the twoD. virilishistone lociin vivo. Further, CLAMP interacts with theD. virilis H3/H4promoterin vitro, even when the poorly-conserved GA-richciselements are deleted, indicating that the protein interacts differently with theD. virilispromoter than it does with theD. melanogasterpromoter. Since CLAMP and MSL2 directly interact inD. melanogaster, we propose thatD. virilisCLAMP recruits MSL2 to an ectopic autosomal site through interaction with X-likeciselements. Further, localization of MSL2 to one of theD. virilishistone loci suggests that the loci are regulated differently and that males and females have different requirements for histone gene regulation.