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Multiple layers of regulation determine the cellular levels of the Pup ligase PafA in Mycobacterium smegmatis
Author(s) -
Korman Maayan,
Schlussel Shai,
Vishkautzan Marina,
Gur Eyal
Publication year - 2019
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.14278
Subject(s) - biology , mycobacterium smegmatis , proteases , proteolysis , proteasome , microbiology and biotechnology , biochemistry , ubiquitin ligase , protein degradation , dna ligase , degron , ubiquitin , enzyme , gene , mycobacterium tuberculosis , medicine , tuberculosis , pathology
Summary Despite being a destructive process, regulated protein degradation is fundamental for proper cell function. While regulated proteolysis in eukaryotes largely involves the ubiquitin‐proteasome system (UPS), most bacterial species rely on multiple ATP‐dependent proteases, such as the Clp proteases. Mycobacteria and related actinobacterial species also possess a degradation system analogous in its function to the UPS. In this system, a prokaryotic ubiquitin‐like protein (Pup) is conjugated to proteins, thereby marking them for proteasomal degradation. A single ligase, PafA, is responsible for Pup conjugation to many protein targets, thus playing a central role in the Pup‐proteasome system (PPS). In Mycobacterium smegmatis , a model mycobacterial organism where the PPS is essential under starvation conditions, cellular PafA levels change in response to nutrient availability. Indeed, increased PafA levels are observed upon nutrient limitation. We found that a multi‐layered network involving transcriptional, translational and post‐translational regulation determines cellular PafA levels. Induced expression is observed at stationary phase, whereas PafA degradation by the proteasome and ClpCP occurs in exponentially growing cells, as opposed to starved cells. In both growth stages, translation attenuation maintains low PafA expression levels. Altogether, these mechanisms establish the dynamics in PafA levels during bacterial growth.