Nucleic Acids Research Advance Access originally published online on May 31, 2008
Nucleic Acids Research 2008 36(12):4009-4021; doi:10.1093/nar/gkn353
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Nucleic Acids Research, 2008, Vol. 36, No. 12 4009-4021
© 2008 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Eukaryotic HMGB proteins as replacements for HU in E. coli repression loop formation
1Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, 200 First St. SW, Rochester, MN 55905 and 2Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742-2021, USA
*To whom correspondence should be addressed. Tel: +1 507 284 9041; Fax: +1 507 284 2053; Email: maher{at}mayo.edu
Received March 31, 2008. Revised May 16, 2008. Accepted May 16, 2008.
DNA looping is important for gene repression and activation in Escherichia coli and is necessary for some kinds of gene regulation and recombination in eukaryotes. We are interested in sequence-nonspecific architectural DNA-binding proteins that alter the apparent flexibility of DNA by producing transient bends or kinks in DNA. The bacterial heat unstable (HU) and eukaryotic high-mobility group B (HMGB) proteins fall into this category. We have exploited a sensitive genetic assay of DNA looping in living E. coli cells to explore the extent to which HMGB proteins and derivatives can complement a DNA looping defect in E. coli lacking HU protein. Here, we show that derivatives of the yeast HMGB protein Nhp6A rescue DNA looping in E. coli lacking HU, in some cases facilitating looping to a greater extent than is observed in E. coli expressing normal levels of HU protein. Nhp6A-induced changes in the DNA length-dependence of repression efficiency suggest that Nhp6A alters DNA twist in vivo. In contrast, human HMGB2-box A derivatives did not rescue looping.