Robert Sabatini
University of Georgia, USA
Title: Role of O-linked glucose modification of DNA in regulating transcription termination and gene expression in trypanosomatids
Biography
Biography: Robert Sabatini
Abstract
Kinetoplastids are a group of early-diverged eukaryotes that includes the human parasites Trypanosoma brucei, and Leishmania major. The genome of these pathogens contains a modified DNA base (beta-D-glucosyl-hydroxymethyluracil) consisting of O-linked glucose modification of the thymine base such that the glucose moiety sticks out into the major groove of DNA. The modified base, called base J, is synthesized through the hydroxylation of thymidine by a dioxygenase (JBP) forming hydroxymethyluridine, followed by the transfer of a glucose by the glucosyltransferase enzyme JGT. I will present our most recent studies on the synthesis and function of base J, focusing on its role in regulating RNA polymerase II (RNAP II) transcription termination. The genomes of kinetoplastids are organized into polycistronic gene clusters that contain multiple genes that are co-transcribed from a single promoter. We have localized base J at regions flanking the polycistronic clusters at sites involved in initiation and termination and demonstrated that the loss of J results in increased RNAP II recruitment at promoters and transcription of the clusters. We now show that reduction of base J at termination sites within polycistronic gene clusters leads to readthrough transcription and increased expression of downstream genes, including developmentally regulated genes involved in parasite pathogenesis. The current model is that the glucose moiety of base J provides a steric block for transcription elongation stimulating termination. The role of the GTase JGT in regulating the localization of J at specific sites in the genome will also be discussed.