Phylogenetic evidence for the emergence of bacterial σ-factors by domain fusion
- 1National Centre for Biological Sciences, Tata Institute of Fundamental Research, Bengaluru, 560065, India
Abstract
{sigma}-factors are dissociable subunits of RNA polymerase (RNAP), forming the basal regulatory machinery for bacterial transcription. The minimal {sigma}-factors contain two domains (called {sigma}2 or {sigma}4), both of which bind RNAP as well as the promoter DNA through their helix-turn-helix motif. Housekeeping {sigma}-factors contain four domains. We identify proteins containing at least one of the four {sigma}-factor domains in bacterial and bacteriophage genomes; we also show that proteins containing either {sigma}2 or {sigma}4, which are not defined as {sigma}-factors, are commonly found in both sets of organisms. Using phylogenetic analysis of these two domains, we suggest that the highly conserved major housekeeping {sigma}-factor, with its complex domain architecture, represents a late-evolving monophyletic clade, whereas single-domain proteins and minimal {sigma}-factor architectures comprising {sigma}2 and {sigma}4 might be ancestral. Thus, {sigma}-factors probably evolved from single-domain DNA-binding transcription factors by domain accretion.
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BibTeX
@misc{tiwary2026phylogenetic,
title = {{Phylogenetic evidence for the emergence of bacterial σ-factors by domain fusion}},
author = {P. Tiwary and A. S. N. Seshasayee},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.08.757525},
url = {https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Phylogenetic evidence for the emergence of bacterial σ-factors by domain fusion
AU - P. Tiwary
AU - A. S. N. Seshasayee
PY - 2026
DA - 2026/10/08
PB - bioRxiv
DO - 10.64898/2026.10.08.757525
UR - https://www.biorxiv.org/content/10.64898/2026.10.08.757525v1
AB - {sigma}-factors are dissociable subunits of RNA polymerase (RNAP), forming the basal regulatory machinery for bacterial transcription. The minimal {sigma}-factors contain two domains (called {sigma}2 or {sigma}4), both of which bind RNAP as well as the promoter DNA through their helix-turn-helix motif. Housekeeping {sigma}-factors contain four domains. We identify proteins containing at least one of the four {sigma}-factor domains in bacterial and bacteriophage genomes; we also show that proteins containing either {sigma}2 or {sigma}4, which are not defined as {sigma}-factors, are commonly found in both sets of organisms. Using phylogenetic analysis of these two domains, we suggest that the highly conserved major housekeeping {sigma}-factor, with its complex domain architecture, represents a late-evolving monophyletic clade, whereas single-domain proteins and minimal {sigma}-factor architectures comprising {sigma}2 and {sigma}4 might be ancestral. Thus, {sigma}-factors probably evolved from single-domain DNA-binding transcription factors by domain accretion.
ER -