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The unique N-terminal region of Mycobacterium tuberculosis sigma factor A plays a dominant role in the essential function of this protein

Singha, B and Behera, D and Khan, MZ and Singh, NK and Sowpati, DT and Gopal, B and Nandicoori, VK (2023) The unique N-terminal region of Mycobacterium tuberculosis sigma factor A plays a dominant role in the essential function of this protein. In: Journal of Biological Chemistry, 299 (3).

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Official URL: https://doi.org/10.1016/j.jbc.2023.102933


SigA (σA) is an essential protein and the primary sigma factor in Mycobacterium tuberculosis (Mtb). However, due to the absence of genetic tools, our understanding of the role and regulation of σA activity and its molecular attributes that help modulate Mtb survival is scant. Here, we generated a conditional gene replacement of σA in Mtb and showed that its depletion results in a severe survival defect in vitro, ex vivo, and in vivo in a murine infection model. Our RNA-seq analysis suggests that σA either directly or indirectly regulates ∼57% of the Mtb transcriptome, including ∼28% of essential genes. Surprisingly, we note that despite having ∼64% similarity with σA, overexpression of the primary-like σ factor SigB (σB) fails to compensate for the absence of σA, suggesting minimal functional redundancy. RNA-seq analysis of the Mtb σB deletion mutant revealed that 433 genes are regulated by σB, of which 283 overlap with the σA transcriptome. Additionally, surface plasmon resonance, in vitro transcription, and functional complementation experiments reveal that σA residues between 132-179 that are disordered and missing from all experimentally determined σA-RNAP structural models are imperative for σA function. Moreover, phosphorylation of σA in the intrinsically disordered N-terminal region plays a regulatory role in modulating its activity. Collectively, these observations and analysis provide a rationale for the centrality of σA for the survival and pathogenicity of this bacillus.

Item Type: Journal Article
Publication: Journal of Biological Chemistry
Publisher: American Society for Biochemistry and Molecular Biology Inc.
Additional Information: The copyright for this article belongs to the Authors.
Keywords: Bacteriology; Proteins; Surface plasmon resonance; Transcription, In-vitro; Mycobacteria; Mycobacterium tuberculosis; N-terminals; Regulation; Siga; Sigb; Sigma factor; Terminal regions; Tuberculosis, RNA
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited: 30 Mar 2023 05:52
Last Modified: 30 Mar 2023 05:52
URI: https://eprints.iisc.ac.in/id/eprint/81163

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