Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Taoyuan, Taiwan
Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
J Bacteriol. 2019 Jan 28;201(4). doi: 10.1128/JB.00681-18. Print 2019 Feb 15.
CovR/CovS is a two-component regulatory system in group A and primarily acts as a transcriptional repressor. The D53 residue of CovR (CovR) is phosphorylated by the sensor kinase CovS, and the phosphorylated CovR protein binds to the intergenic region of to inhibit transcription. Nonetheless, the transcription of and is suppressed in mutants. The T65 residue of CovR is phosphorylated in a CovS-independent manner, and phosphorylation at the D53 and T65 residues of CovR is mutually exclusive. Therefore, how phosphorylation at the D53 and T65 residues of CovR contributes to the regulation of and expression was elucidated. The transcription of and was suppressed in the strain that cannot phosphorylate the D53 residue of CovR (CovR mutant) but restored to levels similar to those of the wild-type strain in the CovR mutant. Nonetheless, inactivation of the T65 residue phosphorylation in the CovR mutant cannot derepress the and transcription, indicating that phosphorylation at the T65 residue of CovR is not required for repressing and transcription. Furthermore, complementation of the CovR protein in the strain that expresses the phosphorylated CovR resulted in the repression of and transcription. Unlike the direct binding of the phosphorylated CovR protein and its inhibition of transcription demonstrated previously, the present study showed that inactivation of phosphorylation at the D53 residue of CovR contributes dominantly in suppressing and transcription. CovR/CovS is a two-component regulatory system in group A (GAS). The D53 residue of CovR is phosphorylated by CovS, and the phosphorylated CovR binds to the intergenic region and acts as the transcriptional repressor. Nonetheless, the transcription of and Rgg-controlled is upregulated in the mutant but inhibited in the mutant. The present study showed that nonphosphorylated CovR protein inhibits and transcription in the presence of the phosphorylated CovR, indicating that nonphosphorylated CovR has a dominant role in suppressing transcription. These results reveal the roles of nonphosphorylated CovR in regulating transcription, which could contribute significantly to invasive phenotypes of mutants.
CovR/CovS 是 A 群中的一个双组份调控系统，主要作为转录阻遏物发挥作用。CovR 的 D53 残基被传感器激酶 CovS 磷酸化，磷酸化的 CovR 蛋白与 intergenic region of 结合，从而抑制 转录。然而，在 突变体中， 与 转录被抑制。CovR 的 T65 残基以 CovS 非依赖性方式发生磷酸化，且 CovR 的 D53 和 T65 残基磷酸化相互排斥。因此，CovR 的 D53 和 T65 残基磷酸化如何调控 与 表达被阐明。在不能磷酸化 CovR 的 D53 残基的菌株（CovR 突变体）中， 与 转录受到抑制，但在 CovR 突变体中，T65 残基磷酸化失活不能使 与 转录去阻遏，表明 CovR 的 T65 残基磷酸化不是抑制 与 转录所必需的。此外，在表达磷酸化 CovR 蛋白的菌株中，CovR 蛋白的 补充导致 与 转录的抑制。与先前直接结合磷酸化 CovR 蛋白并抑制 转录的作用不同，本研究表明 CovR 的 D53 残基磷酸化失活在抑制 与 转录中起主要作用。CovR/CovS 是 A 群（GAS）中的一个双组份调控系统。CovR 的 D53 残基被 CovS 磷酸化，磷酸化的 CovR 结合到 intergenic region of 并作为转录阻遏物发挥作用。然而，在 突变体中， 与 Rgg 调控的 转录上调，但在 突变体中被抑制。本研究表明，在存在磷酸化 CovR 的情况下，非磷酸化 CovR 蛋白抑制 与 转录，表明非磷酸化 CovR 在抑制 转录中起主导作用。这些结果揭示了非磷酸化 CovR 在调控 转录中的作用，这可能对 突变体的侵袭表型有重要贡献。
