View Program - 63rd Annual Drosophila Research Conference

Histone proteins play an essential role in nearly all genomic activities in eukaryotes, from gene regulation to DNA damage repair. In order to perform these functions, the ratio of DNA to histone levels must be kept constant, as deviations from this ratio cause cell cycle arrest and genomic instability. Consequently, a cell must double its histone content during each cell cycle. To meet these regulatory requirements, the histone genes are targeted by a conserved pantheon of chromatin proteins, known collectively as the Histone Locus Body (HLB). Most of the dozens of HLB components have no DNA-binding activity, yet they are able to faithfully locate the histone genes in the early embryo. The HLB must also be maintained at histone genes in adult tissues. How the HLB is initiated in the early embryo and maintained in the adult is a crucial gap in our knowledge of how proper histone gene regulation is achieved. Recently, our lab discovered that a single regulatory element located in the histone3/histone4 bidirectional promoter directs HLB initiation along the entire histone array. However, it is not clear if this cis-element, which consists of GA-dinucleotide repeats, is required to maintain the HLB after initiation. To answer this question, I have designed and cloned a novel transgene that takes advantage of the FLP/FRT recombination system in Drosophila. This transgene allows me to wait for the HLB to initiate in the embryo, then heat shock larvae to induce recombination, removing the GA-repeats. If the ectopic HLB is lost following heat shock, this will suggest that the GA-repeats plays an active role in maintaining the HLB. If the ectopic HLB survives heat shock, this will show that the HLB can be maintained even without the cis-element that initiated it, an equally illuminating result.

Initiating and Maintaining the Histone Locus Body: Two Sides of the Same Coin?