How cells enhance DNA flexibility

ORGN 261

Nicole A. Becker1, Jason D. Kahn, jdkahn@umd.edu2, and L. James Maher III, maher@mayo.edu1. (1) Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905, (2) Department of Chemistry and Biochemistry, University of Maryland, College Park, College of Chemical and Life Sciences, Chemistry Bldg. 091, College Park, MD 20742-2021
The E. coli lac operon provides a classic paradigm for understanding regulation of gene transcription. It is now appreciated that lac promoter repression involves cooperative binding of the bidentate lac repressor tetramer to pairs of lac operators via DNA looping. We have adapted components of this system to create an artificial assay of DNA flexibility in E. coli. This approach allows for systematic study of endogenous and exogenous proteins as architectural factors that enhance apparent DNA flexibility in vivo. We show that the binding of inducer alters both the affinity of lac repressor for DNA and also the geometry of repression loops. Deletion of the E. coli HU protein drastically destabilizes small repression loops, an effect that can be partially overcome by expression of a heterologous mammalian HMG protein. These results emphasize that the inherent inflexibility of DNA restrains looping and must be modulated in vivo.
 

Frontiers in Bio-organic Chemistry and Chemical Biology
8:00 AM-11:55 AM, Monday, 14 March 2005 Convention Center -- Ballroom 20 C-D, Oral

Division of Organic Chemistry

The 229th ACS National Meeting, in San Diego, CA, March 13-17, 2005