Involvement of protein acetylation in glucose‐induced transcription of a stress‐responsive promoter

Abstract

Summary In eukaryotes, lysine acetylation is a well-established posttranslational modification that has been implicated in virtually all aspects of eukaryotic physiology. Although homologs of the enzymes that catalyze protein acetylation are widely conserved and distributed amongst bacterial species, not much is known about the impact of protein acetylation on bacterial physiology. Here, we present evidence that the Gcn5-like acetyltransferase YfiQ and the sirtuin deacetylase CobB play crucial roles in the transcription regulation of the periplasmic stress-responsive promoter cpxP when cells of Escherichia coli grow in the presence of glucose, an environment that induces protein acetylation. Under this growth condition, several acetylation sites were detected on three of the RNA polymerase (RNAP) subunits: β, β’ and α. We focused on acetylations of the carboxy-terminal domain (CTD) of α because of its relative small size and its limited acetylation. We determined that K298 of α is acetylated in a glucose and YfiQ-dependent manner and that K298 is specifically required for glucose-induced cpxP transcription. Since the αCTD aids in promoter recognition by RNA polymerase, we propose its acetylation may influence bacterial physiology through effects on gene expression.

Inhibition of Acetyl Phosphate-dependent Transcription by an Acetylatable Lysine on RNA Polymerase

“…proposed that glucose-induced cpxP transcription requires Lys-298 on the surface of the ␣CTD and seems to be regulated by a reversible acetylation event mediated by the acetyltransferase YfiQ and the deacetylase CobB (15). The knowledge that glucose-induced cpxP transcription does not require the sensor kinase CpxA, but requires the cognate response regulator CpxR (8) led us to re-investigate the role of CpxR in this response.…”

“…For several reasons, we considered the possibility that AcCoA could function as this inhibitor, perhaps by acting as an acetyl-donor. First, the concentration of AcCoA has been shown to rapidly increase when E. coli cells are exposed to glucose (30) and growth in the presence of 0.4% glucose causes a general increase in protein acetylation (15). Second, pta mutants excrete large amounts of pyruvate and lactate in an AcCoA-sensitive manner (31), suggesting that disruption of the Pta-AckA pathway causes a metabolic imbalance that could affect the AcCoA pool.…”

“…12). One such behavior is the CpxA-independent induction of cpxP transcription that occurs when glucose is added to tryptone-based growth media (8,14,15). If a behavior strictly depends on AcP to donate its phosphoryl group to a response regulator, then an ackA mutant, which accumulates AcP (16), should elicit behavior opposite to that exhibited by a pta mutant, which cannot synthesize AcP (16).…”

“…We also presented evidence that nearly 30 lysine residues on three different RNAP subunits are acetylated in a glucose-and YfiQ-dependent manner. One of these acetylated lysines (the surface-exposed Lys-298 of the ␣ subunit) is required for glucose-induced cpxP transcription (15).…”

“…17) that does not appear to be an acetylation target (15). On the basis of OmpR homology, phosphorylation of Asp-51 of CpxR is predicted to induce a conformational change that promotes gene regulation (17).…”