Transcription antitermination by translation initiation factor IF1

Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA, Waksman Institute, Department of Biochemistry and Molecular Biology, Rutgers, The State University of New Jersey, 190 Frelinghuysen Road, Piscataway, NJ 08854,USA, Basic Research Program, SAIC-Frederick, Inc., NCI-Frederick, Frederick, MD 21702, Molecular Control and Genetics Section, Gene Regulation and Chromosome Biology Laboratory, Center for Cancer Research, National Cancer Institute at Frederick, Frederick, MD 21702, Department of Microbiology and Immunology, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA

	Abstract

Bacterial translation initiation factor IF1 is an S1 domain protein that belongs to the oligomer binding (OB) fold proteins. Cold-Shock-Domain (CSD) containing proteins such as CspA (major cold shock protein of Escherichia coli) and its homologues also belong to the OB fold protein family. The striking structural similarity between IF1 and CspA homologues suggests a functional overlap between these proteins. Certain members of the CspA family of cold shock proteins act as nucleic acid chaperones: they melt secondary structures in nucleic acids and act as transcription antiterminators. This activity may help the cell to acclimatize to low temperature, since cold-induced stabilization of secondary structures in nascent RNA can impede transcription elongation. Here, we show that E. coli translation initiation factor, IF1, also has RNA chaperone activity and acts as transcription antiterminator in vivo and in vitro. We further show that the RNA chaperone activity of IF1, although critical for transcription antitermination, is not essential for its role in supporting cell growth that is presumably in translation. The results thus indicate that IF1 may participate in transcription regulation and there may exist a cross-talk and/or functional overlap between the Csp family proteins, known to be involved in transcription regulation at cold shock, and S1 domain proteins, known to function in translation.