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Journal of Bacteriology, March 2002, p. 1565-1570, Vol. 184, No. 6
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.6.1565-1570.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

The Histone-Like Protein HU Does Not Obstruct Movement of T7 RNA Polymerase in Escherichia coli Cells but Stimulates Its Activity

Pilar Morales,1 Josette Rouviere-Yaniv,1* and Marc Dreyfus2

Laboratoire de Physiologie Bactérienne (CNRS, UPR 9073), Institut de Biologie Physico-Chimique, 75005 Paris,1 Laboratoire de Génétique Moléculaire (CNRS UMR 8541), ENS, 75230 Paris, France2

Received 13 April 2000/ Accepted 7 December 2001

In vivo, RNA polymerases (RNAPs) do not transcribe naked DNA but do transcribe protein-associated DNA. Studies with the model enzyme T7 RNAP have shown that, in eukaryotic cells or in vitro, nucleosomes can inhibit both transcription initiation and elongation. We examine here whether the presence of HU, one of the major histone-like proteins in Escherichia coli cells (the genuine milieu for T7 RNAP) affects its activity. An engineered lac operon fused to the T7 late promoter was introduced into the chromosome of T7 RNAP-producing strains that either overexpress HU or lack it. The flows of RNAP that enter and exit this operon were compared with regard to the content of HU. We found that the fraction of T7 RNAP molecules that do not reach the end of the lac operon (ca. 15%) is the same whether the host cells overexpressed HU or lacked it: thus, the enzyme either freely displaces HU or transcribes through it. However, in these cells, the transcript yield was increased when HU is overexpressed and decreased in the hup mutants, presumably reflecting changes in DNA supercoiling. Thus, in contrast to eukaryotic nucleosomes, HU does not impair T7 RNAP activity but has a stimulatory effect. Finally, our results suggest that HU can also influence mRNA stability in vivo.

* Corresponding author. Mailing address: Laboratoire de Physiologie Bactérienne (CNRS, UPR 9073), Institut de Biologie Physico-Chimique, 13 Rue Pierre et Marie Curie, 75005 Paris, France. Phone: 33-1-58-41-51-45. Fax: 33-1-58-41-50-20. E-mail: yaniv{at}ibpc.fr.

Journal of Bacteriology, March 2002, p. 1565-1570, Vol. 184, No. 6
0021-9193/02/$04.00+0     DOI: 10.1128/JB.184.6.1565-1570.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Kamashev, D., Balandina, A., Mazur, A. K., Arimondo, P. B., Rouviere-Yaniv, J. (2008). HU binds and folds single-stranded DNA. Nucleic Acids Res 36: 1026-1036 [Abstract] [Full Text]  
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  • van Noort, J., Verbrugge, S., Goosen, N., Dekker, C., Dame, R. T. (2004). Dual architectural roles of HU: Formation of flexible hinges and rigid filaments. Proc. Natl. Acad. Sci. USA 101: 6969-6974 [Abstract] [Full Text]  
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