Increased RNA polymerase availability directs resources towards growth at the expense of maintenance

TY - JOUR

T1 - Increased RNA polymerase availability directs resources towards growth at the expense of maintenance

AU - Gummesson, Bertil

AU - Magnusson, Lisa U.

AU - Lovmar, Martin

AU - Kvint, Kristian

AU - Persson, Örjan

AU - Ballesteros, Manuel

AU - Farewell, Anne

AU - Nyström, Thomas

PY - 2009/8/1

Y1 - 2009/8/1

N2 - Nutritionally induced changes in RNA polymerase availability have been hypothesized to be an evolutionary primeval mechanism for regulation of gene expression and several contrasting models have been proposed to explain how such 'passive' regulation might occur. We demonstrate here that ectopically elevating Escherichia coli RNA polymerase (Eσ70) levels causes an increased expression and promoter occupancy of ribosomal genes at the expense of stress-defense genes and amino acid biosynthetic operons. Phenotypically, cells overproducing Eσ70 favours growth and reproduction at the expense of motility and damage protection; a response reminiscent of cells with no or diminished levels of the alarmone guanosine tetraphosphate (ppGpp). Consistently, we show that cells lacking ppGpp displayed markedly elevated levels of free Eσ70 compared with wild-type cells and that the repression of ribosomal RNA expression and reduced growth rate of mutants with constitutively elevated levels of ppGpp can be suppressed by overproducing Eσ70. We conclude that ppGpp modulates the levels of free Eσ70 and that this is an integral part of the alarmone's means of regulating a trade-off between growth and maintenance.

AB - Nutritionally induced changes in RNA polymerase availability have been hypothesized to be an evolutionary primeval mechanism for regulation of gene expression and several contrasting models have been proposed to explain how such 'passive' regulation might occur. We demonstrate here that ectopically elevating Escherichia coli RNA polymerase (Eσ70) levels causes an increased expression and promoter occupancy of ribosomal genes at the expense of stress-defense genes and amino acid biosynthetic operons. Phenotypically, cells overproducing Eσ70 favours growth and reproduction at the expense of motility and damage protection; a response reminiscent of cells with no or diminished levels of the alarmone guanosine tetraphosphate (ppGpp). Consistently, we show that cells lacking ppGpp displayed markedly elevated levels of free Eσ70 compared with wild-type cells and that the repression of ribosomal RNA expression and reduced growth rate of mutants with constitutively elevated levels of ppGpp can be suppressed by overproducing Eσ70. We conclude that ppGpp modulates the levels of free Eσ70 and that this is an integral part of the alarmone's means of regulating a trade-off between growth and maintenance.

KW - Passive regulation

KW - ppGpp

KW - RNA polymerase

KW - Stringent control

KW - Transcriptional trade-off

UR - http://www.scopus.com/inward/record.url?scp=68249138705&partnerID=8YFLogxK

U2 - 10.1038/emboj.2009.181

DO - 10.1038/emboj.2009.181

M3 - Journal article

C2 - 19574956

AN - SCOPUS:68249138705

SN - 0261-4189

VL - 28

SP - 2209

EP - 2219

JO - E M B O Journal

JF - E M B O Journal

IS - 15

ER -