Nuclear bodies are membraneless structures containing concentrated regulatory factors that coordinate nuclear processes such as gene expression. The histone locus body (HLB) is a discrete nuclear body that is the main site of histone mRNA production. While many factors of the HLB are known, there are many unknown factors. In addition, while HLB function is highly conserved, it is also unknown how the HLB has changed and evolved in different species. The histone locus (HL) of the model organism Drosophila melanogaster contains ~100 tandem arrays of the five histone genes. While D. melanogaster has one HL, the related species Drosophila virilis, has two HL. We observe localization of the male-specific dosage compensation protein MSL2 to one of the two D. virilis histone loci using polytene chromosome immunofluorescence, which we do not observe in other Drosophila species. In order to confirm our immunofluorescence observations, we mapped existing MSL2 ChIP-seq data and discovered that when MSL2 from either species is overexpressed, it targets the H2a-H2b promoter. We immunostained transgenic flies carrying an H2a-H2b promoter transgene to determine if MSL2 targets this region when outside the context of the histone locus. We do not see the same HL localization when MSL2 is expressed at wild-type levels. Finally, we performed RNA isolation and qPCR analysis on four Drosophila species to compare expression levels of msl2. Our results indicate that MSL2 may be playing a different role at the HL in different Drosophila species. Overall, this gives us better insight on histone gene regulation.
Support or Funding Information
This work was supported by an Emory Summer Undergraduate Research Experience (SURE) Fellowship to M.X., T32GM00008490 and F31HD105452 to L.J.H., and R00HD092625 and R35GM142724 to L.E.R.
