Poster abstracts

Poster number 26 submitted by Barbare Khitiri

The ω subunit of RNA polymerase is more than just a chaperone

Barbare Khitiri (Microbiology), Irina Artsimovitch (Microbiology)

Abstract:
Escherichia coli RNA polymerase (RNAP) core enzyme consists of five subunits, αI, αII, β, β’ and ω. Even though functions of αI, αII, β, and β’ in catalysis and regulation are well established, ω is thought, act only as a chaperone. Several lines of evidence suggest that ω modulates RNAP catalysis, stress response and interactions with accessory factors. First, ω binds to transcription factors NusA and SspA and to a stress alarmone ppGpp and decreases Rho-dependent termination. Second, the deletion of rpoZ, the gene that encodes ω, confers sensitivity to acidic stress and alters RNAP distribution within stress-associated xenogenes. Third, altered ω/β’ interactions appear to trap RNAP in an inactive state; for example, a dominant-lethal N60D substitution in ω that increases its helicity and rigidity is thought to restrict β’ dynamics. The phenotype is rescued by β’ Y457S substitution adjacent to the catalytic Asp triad, suggesting communication between ω and RNAP active site. My preliminary data show that ω confers differences in intrinsic cleavage, suggesting possible effects on fidelity. I also found that Δω RNAP was hypersensitive to NusA, an essential transcription elongation factor. In contrast, Δω RNAP responded to accessory factors GreB and RfaH similarly to the wild-type RNAP.

References:
Mittermeier et al. (2022) A non-native C-terminal extension of the β’ subunit compromises RNA polymerase and Rho functions. Mol Biol. 117:871-885.

Molodtsov et al. (2018) Allosteric Effector ppGpp Potentiates the Inhibition of Transcript by DksA Molecular cell 69, 828-839.

Nelly Said et al. (2021) Steps toward translocation-independent RNA polymerase inactivation by terminator ATPase ρ. Science 371, eabd1673.

Sarkar et al. (2013) Inactivation of the Bacterial RNA Polymerase Due to Acquisition of Secondary Structure by the ω Subunit. Journal of biological chemistry 25076.

Yamamoto, K. et al. (2018) Altered Distribution of RNA Polymerase Lacking the Omega Subunit within Prophaes along the Escherichia coli K-12 Genome Molecular biology and physiology.

Keywords: omega subunit , RNA polymerase, transcription catalysis and regulation