December 3, 2013, 4:00 PM, T-639, Health Sciences Building
Sue Lovett, Ph.D.
Abraham S. and Gertrude burg Professor of Microbiology
Department of Biology, Rosenstiel Basic Medical Sciences Research Center
DNA dynamics and the bacterial stringent response
The bacterial "stringent response" is a coordinated response to a variety of starvation conditions, characterized by the accumulation of the intracellular signaling molecule, ppGpp. By direct binding to RNA polymerase, ppGpp reprograms transcription such stable RNA species such as rRNA and tRNA are down-regulated and biosynthetic genes are up-regulated. Less well understood is the impact of ppGpp on cell cycle events, and in particular, on DNA metabolism. Using E. coli as a model system, we have investigated the mechanisms by which the stringent response regulates DNA replication and repair, chromosome condensation and segregation. We find that accumulation of ppGpp blocks DNA replication at the level of initiation induces an SOS-independent DNA damage response dependent on RpoS, blocks segregation of chromosome termini and induces a highly decondensed nucleoid state. Our genetic analysis suggests that E. coli integrates signals of ongoing replication, DNA damage and starvation to maximize survival under stressful conditions. Further elucidation of the mechanisms of these effects should reveal important information about how bacteria survive nutritional downturns
December 10, 2013, 4:00 PM, T-639, Health Sciences Building
Rich Condit, Ph.D.
Professor, Department of Molecular Genetics and Microbiology
University of Florica
Transcriptional regulation of poxvirus gene expression
Vaccinia is a large double stranded DNA-containing poxvirus that replicates in the cytoplasm of infected cells. The cytoplasmic site of replication requires that the virus encode virtually all of the functions required for both mRNA and DNA metabolism. Thus over the years vaccinia has served as a very useful model system for understanding mRNA synthesis and modification.
Transcription elongation is an important control point for regulation of eukaryotic gene expression. Our work demonstrates that postreplicative viral gene transcription elongation and termination is regulated by a complex of virus coded protein factors during vaccinia infection. A study of this regulation is important for understanding regulation of vaccinia virus gene expression in particular, and the system may prove to be an important model for study of regulation of transcription elongation in eukaryotes in general.