title: Inhibition of Mycobacterium tuberculosis RNA polymerase by binding of a Gre factor homolog to the secondary channel.
abstract: Because of its essential nature, each step of transcription, viz., initiation, elongation, and termination, is subjected to elaborate regulation. A number of transcription factors modulate the rates of transcription at these different steps, and several inhibitors shut down the process. Many modulators, including small molecules and proteinaceous inhibitors, bind the RNA polymerase (RNAP) secondary channel to control transcription. We describe here the first small protein inhibitor of transcription in Mycobacterium tuberculosis. Rv3788 is a homolog of the Gre factors that binds near the secondary channel of RNAP to inhibit transcription. The factor also affected the action of guanosine pentaphosphate (pppGpp) on transcription and abrogated Gre action, indicating its function in the modulation of the catalytic center of RNAP. Although it has a Gre factor-like domain organization with the conserved acidic residues in the N terminus and retains interaction with RNAP, the factor did not show any transcript cleavage stimulatory activity. Unlike Rv3788, another Gre homolog from Mycobacterium smegmatis, MSMEG_6292 did not exhibit transcription-inhibitory activities, hinting at the importance of the former in influencing the lifestyle of M. tuberculosis.
authors.affiliation: Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore, India.
authors.forename: Arnab
authors.initials: A
authors.lastname: China
authors.forename: Sonakshi
authors.initials: S
authors.lastname: Mishra
authors.forename: Priyanka
authors.initials: P
authors.lastname: Tare
authors.forename: Valakunja
authors.initials: V
authors.lastname: Nagaraja
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006158:Guanosine Pentaphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D020102:Mycobacterium smegmatis / Q000201:enzymology / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D006158:Guanosine Pentaphosphate; D012321:DNA-Directed RNA Polymerases