RT Journal Article
SR Electronic
T1 Direct proteolytic control of an extracytoplasmic function RNA polymerase sigma factor
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 576462
DO 10.1101/576462
A1 Bohdan Bilyk
A1 Sora Kim
A1 Tania A. Baker
A1 Ryan F. Seipke
YR 2019
UL http://biorxiv.org/content/early/2019/03/14/576462.abstract
AB The survival of any microbe relies upon its ability to respond to environmental change. Use of Extra Cytoplasmic Function (ECF) RNA polymerase sigma (σ) factors is a major strategy enabling such signal transduction. Streptomyces species harbour a large number of ECF σ factors; nearly all of which regulate genes required for morphological differentiation and/or response to environmental stress, except for σAntA, which regulates starter-unit biosynthesis in the production of antimycin, an anticancer compound. Unlike a canonical ECF σ factor, whose activity is regulated by a cognate anti-σ factor, σAntA is an orphan, raising intriguing questions about how its activity may be controlled. Here, we reconstitute in vitro ClpXP proteolysis of σAntA, but not a variant lacking a C-terminal di-alanine motif. Furthermore, we show that the abundance of σAntA in vivo is enhanced by removal of the ClpXP recognition sequence, and that levels of the protein rise when cellular ClpP-protease activity is abolished. These data establish direct proteolysis as an alternative and thus far unique control strategy for an ECF RNA polymerase σ factor and expands the paradigmatic understanding of microbial signal transduction regulation.Importance Most antibiotics are derived from secondary metabolites produced by Streptomyces species. The recent rise in the number of bacterial infections resistant to antibiotics has led to renewed interest in discovery of new secondary metabolites produced by these microbes. An average species of Streptomyces harbours ~30 biosynthetic pathways, but the majority of them are not in the laboratory. A key approach is therefore activation of these “silent” pathways, but new insights into how their expression is regulated are required. Our findings reveal that the ECF σ factor (σAntA) that regulates antimycin biosynthesis lacks an anti-σ partner and instead is controlled by the Clp-protease system. These data establish direct proteolysis as a novel strategy for the control of ECF RNA polymerase σ factors and will aid the pursue of silent biosynthetic pathways.