Poster abstracts
Poster number 153 submitted by Alexander Yakhnin
NusG is a sequence-specific RNA polymerase pause factor
Alexander V. Yakhnin (Dept. of Biochemistry and Molecular Biology, Pennsylvania State University), Paul Babitzke (Dept. of Biochemistry and Molecular Biology, Pennsylvania State University)
Abstract:
NusG, which is referred to as Spt5 in archaeal and eukaryotic organisms, is the only transcription factor conserved in all three domains of life. This transcription elongation factor binds to RNA polymerase (RNAP) and assists in DNA-templated RNA synthesis. Data obtained from studies of E. coli NusG (NusGEc) indicate that this protein is capable of increasing transcription processivity by suppressing RNAP pausing. In contrast to E. coli, B. subtilis NusG (NusGBs) dramatically stimulates pausing at two sites in the untranslated leader of the B. subtilis trp operon. These two regulatory pause sites participate in transcription attenuation and translational control mechanisms, respectively. Transcription elongation complexes reconstituted in vitro with nucleic acid scaffolds revealed that NusGBs makes sequence-specific contacts with a T-rich sequence in the non-template DNA strand within the paused transcription bubble. NusGBs protects T residues of the recognition sequence from permanganate oxidation and the degree of protection correlates with the pause-simulation activity. The amino acid sequences of two short regions within the N-terminal domain of NusGBs are primarily responsible for specific recognition of the trp pause signals. The finding that these amino acid sequences are not conserved in NusGEc explains why the E. coli protein is not capable of stimulating pausing at the B. subtilis trp pause sites. E. coli also contains a NusG paralog called RfaH, which is recruited to the transcription elongation complex through recognition of the ops sequence in the non-template DNA strand. The ops site-recognizing amino acid residues of RfaH (Belogurov et al., 2010) are located in the same regions that we identified for NusGBs. Our results suggest that recognition of specific sequences in non-template DNA and stimulation of RNAP pausing is a conserved function of NusG/Spt5-like transcription factors.
References:
Belogurov, G.A., Sevostyanova, A., Svetlov, V., and Artsimovitch, I. (2010) Functional regions of the N-terminal domain of the antiterminator RfaH. Mol. Microbiol. 76:286-301.
Keywords: transcription factor, RNAP pausing, non-template DNA