title: Co-evolution of RNA polymerase with RbpA in the phylum Actinobacteria.
abstract: The role of RbpA in the backdrop ofM. smegmatisshowed that it rescues mycobacterial RNA polymerase from rifampicin-mediated inhibition (Dey et al., 2010; Dey et al., 2011). Paget and co-workers (Paget et al., 2001; Newell et al., 2006) have revealed that RbpA homologs occur exclusively in actinobacteria. Newell et al. (2006) showed that MtbRbpA, when complemented in a ∆rbpAmutant ofS. coelicolor, showed a low recovery of MIC (from 0.75 to 2 μg/ml) as compared to complementation by native RbpA ofS. coelicolor(MIC increases from 0.75 to 11 μg/ml). Our studies on MsRbpA show that it is a differential marker forM. smegmatisRNA polymerase as compared toE. coliRNA polymerase at IC50levels of rifampicin. A recent sequence-based analysis by Lane and Darst (2010) has shown that RNA polymerases from Proteobacteria and Actinobacteria have had a divergent evolution.E. coliis a representative of Proteobacteria andM. smegmatisis an Actinobacterium. RbpA has an exclusive occurrence in Actinobacteria. Since protein-protein interactions might not be conserved across different species, therefore, the probable reason for the indifference of MsRbpA towardE. coliRNA polymerase could be the lineage-specific differences between actinobacterial and proteobacterial RNA polymerases. These observations led us to ask the question as to whether the evolution of RbpA in Actinobacteria followed the same route as that of RNA polymerase subunits from actinobacterial species. We show that the exclusivity of RbpA in Actinobacteria and the unique evolution of RNA polymerase in this phylum share a co-evolutionary link. We have addressed this issue by a blending of experimental and bioinformatics based approaches. They comprise of induction of bacterial cultures coupled to rifampicin-tolerance, transcription assays and statistical comparison of phylogenetic trees for different pairs of proteins in actinobacteria.
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560012, India.
authors.forename: Abhinav
authors.initials: A
authors.lastname: Dey
authors.affiliation: Department of Plant Molecular Biology and Biotechnology, Center for Plant Molecular Biology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India.
authors.forename: V R
authors.initials: VR
authors.lastname: Adithi
authors.affiliation: Molecular Biophysics Unit, Indian Institute of Science, Bangalore-560012, India.
authors.forename: Dipankar
authors.initials: D
authors.lastname: Chatterji
keywords: Actinobacteria; Antibiotic tolerance; Coevolution; Protein–protein interaction; RNA polymerase; RbpA; Rifampicin; Transcription