Molecular analysis of components in Drosophila polycomb group silencing.

University of Minnesota Ph.D. dissertation. April 2009. Major: Biochemistry, Molecular Biology, and Biophysics. Advisor: Jeffrey A Simon. 1 computer file (PDF; viii, 191 pages, appendices I-IV. ill. (some col.)) + 25 supplemental files (PDF; figures)The aim of this research is to describe the molecular mechanism used by a set of regulatory proteins, called Polycomb Group proteins, to silence genes. In general, the function of the Polycomb Group is to silence cell differentiation factors in the course of embryonic development by operating on chromatin. First, we investigate a recently discovered Polycomb protein to determine its expression profile during development and to establish its role within a complex of proteins that methylates chromatin during Polycomb repression. Second, we target the methyltransferase complex to artificial loci on chromosomes by fusing one of its subunits to a heterologous DNA-binding domain. Third, we investigate the recruitment of the SCM Polycomb Group protein to chromatin during silencing. We perform molecular epistasis experiments to determine the dependencies between SCM and the other Polycomb Group proteins for arriving at chromatin. These studies use the Drosophila model system. The experiments include the observation of phenotypes resulting from genetic crosses and modifications, immunostaining of tissues and chromosomes, and chromatin immunoprecipitation. The Polycomb Group of proteins is highly conserved from Drosophila to humans, so the results of this research should yield insights about gene regulation in all higher organisms