Laboratory of Molecular Microbiology, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 08826, Korea.
Center for RNA Research, Institute for Basic Science, Seoul 08826, Korea.
Nucleic Acids Res. 2020 Mar 18;48(5):2401-2411. doi: 10.1093/nar/gkaa011.
Protein lysine acetylation, one of the most abundant post-translational modifications in eukaryotes, occurs in prokaryotes as well. Despite the evidence of lysine acetylation in bacterial RNA polymerases (RNAPs), its function remains unknown. We found that the housekeeping sigma factor (HrdB) was acetylated throughout the growth of an actinobacterium, Streptomyces venezuelae, and the acetylated HrdB was enriched in the RNAP holoenzyme complex. The lysine (K259) located between 1.2 and 2 regions of the sigma factor, was determined to be the acetylated residue of HrdB in vivo by LC-MS/MS analyses. Specifically, the label-free quantitative analysis revealed that the K259 residues of all the HrdB subunits were acetylated in the RNAP holoenzyme. Using mutations that mimic or block acetylation (K259Q and K259R), we found that K259 acetylation enhances the interaction of HrdB with the RNAP core enzyme as well as the binding activity of the RNAP holoenzyme to target promoters in vivo. Taken together, these findings provide a novel insight into an additional layer of modulation of bacterial RNAP activity.
蛋白质赖氨酸乙酰化是真核生物中最丰富的翻译后修饰之一，也发生在原核生物中。尽管有证据表明细菌 RNA 聚合酶（RNAP）中存在赖氨酸乙酰化，但它的功能仍然未知。我们发现，管家西格玛因子（HrdB）在放线菌变栖裂脂单胞菌的整个生长过程中被乙酰化，并且乙酰化的 HrdB 在 RNAP 全酶复合物中富集。通过 LC-MS/MS 分析，确定位于西格玛因子 1.2 和 2 区域之间的赖氨酸（K259）是 HrdB 体内的乙酰化残基。具体来说，无标记定量分析显示，RNAP 全酶中所有 HrdB 亚基的 K259 残基都被乙酰化。使用模拟或阻断乙酰化的突变（K259Q 和 K259R），我们发现 K259 乙酰化增强了 HrdB 与 RNAP 核心酶的相互作用以及 RNAP 全酶在体内与靶启动子的结合活性。总之，这些发现为细菌 RNAP 活性的另一种调节方式提供了新的见解。
