Toxin YafQ Reduces Escherichia coli Growth at Low Temperatures.

PLoS One

Department of Chemical Engineering, Pennsylvania State University, University Park, Pennsylvania, 16802-4400, United States of America.

Published: July 2017

AI Article Synopsis

  • Toxin/antitoxin systems, like the YafQ/DinJ system in E. coli, help reduce cell metabolism during stress, with toxin YafQ cleaving specific RNA transcripts to slow growth.
  • Deleting the antitoxin gene dinJ led to slower growth and reduced metabolism at lower temperatures (18°C), while this effect was not observed at 37°C; adding DinJ back from a plasmid restored growth.
  • Mutations that inactivated YafQ were discovered to reverse the growth slowdown, and it was found that YafQ is particularly toxic at low temperatures with Mlc acting as a counter to its effects.

Article Abstract

Toxin/antitoxin (TA) systems reduce metabolism under stress; for example, toxin YafQ of the YafQ/DinJ Escherichia coli TA system reduces growth by cleaving transcripts with in-frame 5'-AAA-G/A-3' sites, and antitoxin DinJ is a global regulator that represses its locus as well as controls levels of the stationary sigma factor RpoS. Here we investigated the influence on cell growth at various temperatures and found that deletion of the antitoxin gene, dinJ, resulted in both reduced metabolism and slower growth at 18°C but not at 37°C. The reduction in growth could be complemented by producing DinJ from a plasmid. Using a transposon screen to reverse the effect of the absence of DinJ, two mutations were found that inactivated the toxin YafQ; hence, the toxin caused the slower growth only at low temperatures rather than DinJ acting as a global regulator. Corroborating this result, a clean deletion of yafQ in the ΔdinJ ΔKmR strain restored both metabolism and growth at 18°C. In addition, production of YafQ was more toxic at 18°C compared to 37°C. Furthermore, by overproducing all the E. coli proteins, the global transcription repressor Mlc was found that counteracts YafQ toxicity only at 18°C. Therefore, YafQ is more effective at reducing metabolism at low temperatures, and Mlc is its putative target.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4996492PMC
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0161577PLOS

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