Transfer–messenger RNA controls the translation of cell‐cycle and stress proteins in Streptomyces

Abstract

The transfer-messenger RNA (tmRNA)-mediated trans-translation mechanism is highly conserved in bacteria and functions primarily as a system for the rescue of stalled ribosomes and the removal of aberrantly produced proteins. Here, we show that in the antibiotic-producing soil bacterium Streptomyces coelicolor, trans-translation has a specialized role in stress management. Analysis of proteins that were carboxy-terminally His 8 -tagged by a recombinant tmRNA identified only 10 targets, including the stress proteins: DnaK heat-shock protein 70, thiostrepton-induced protein A, universal stress protein A, elongation factor Tu3, and the cell-cycle control proteins DasR, SsgA, SsgF and SsgR. Although tmRNA-tagged proteins are degraded swiftly, the translation of dnaK and dasR messenger RNAs (mRNAs) depends fully on tmRNA, whereas transcription is unaffected. The data unveil a surprisingly dedicated functionality for tmRNA, promoting the translation of the same mRNA it targets, at the expense of sacrificing the first nascent protein. In streptomycetes, tmRNA has evolved into a dedicated task force that ensures the instantaneous response to the exposure to stress.

A novel function of Streptomyces integration host factor (sIHF) in the control of antibiotic production and sporulation in Streptomyces coelicolor

“…Their saprophytic life style and complex life cycle necessitates complex transcriptional control, exerted by well-studied regulators such as AdpA (which responds to the c-butyrolactone A-factor), the cAMP receptor protein CRP (pleiotropic regulator of germination and early growth), the nutrient sensor DasR (switch to development), the global amino acid regulator NdgR and the developmental Bld and Whi regulators (Bibb 1996;Flardh and Buttner 2009;Ohnishi et al 2005;Piette et al 2005;Rigali et al 2006;van Wezel et al 2009;Yang et al 2009). A second category of regulators globally affects gene regulation at the level of translation, most notably the rare leucyl-tRNA BldA, which relates to developmental control of TTA-containing genes (Lawlor et al 1987), and tmRNA, which is essential for the translation of antibiotic-and stressrelated genes such as dnaK, dasR, ssgRA and tipA (Barends et al 2010).…”

The σ R regulon of Streptomyces coelicolor A3(2) reveals a key role in protein quality control during disulphide stress

“…The importance of Lon in coping with oxidative stress-induced protein aggregation has been established in mitochondria (Bota & Davies, 2002). Interestingly, it has recently been shown that ssrA, which encodes transfer-messenger RNA (tmRNA) and is controlled in part by sigR, positively controls dnaK, suggesting a more direct link between s R activity and dnaK expression (Barends et al, 2010). In summary, s R plays a more significant role in protein quality control than previously realized, through the control of enzymes such as thiol-disulphide reductases, methionine sulphoxide reductase and AAA+ proteases.…”

The tmRNA ribosome-rescue system

“…Several groups have developed tmRNA variants that encode various epitope tags that are resistant to proteolysis (Fig. 2 and Section III) (Barends et al, 2010; Fujihara et al, 2002; Gottesman et al, 1998; Roche and Sauer, 2001; Thibonnier et al, 2008; Yang and Glover, 2009). These tmRNA variants allow tagging activity to be assessed by immunoblot and have facilitated the identification of several ssrA-tagged proteins in a variety of bacteria (Barends et al, 2010; Collier et al, 2002; Fujihara et al, 2002; Roche and Sauer, 2001).…”