Bacillus subtilis YlxR, Which Is Involved in Glucose-Responsive Metabolic Changes, Regulates Expression of tsaD for Protein Quality Control of Pyruvate Dehydrogenase
Bacillus subtilis YlxR, Which Is Involved in Glucose-Responsive Metabolic Changes, Regulates Expression of tsaD for Protein Quality Control of Pyruvate Dehydrogenase
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DOI：
10.3389/fmicb.2019.00923
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发表时间：
2019-05-01
影响因子：
5.2
通讯作者：
Abe, Kimihiro
中科院分区：
文献类型：
--
作者：
Ogura, Mitsuo;Sato, Tsutomu;Abe, Kimihiro
葡萄糖是许多细菌最有利的碳源，它们有多个葡萄糖响应基因网络。最近，我们发现在枯草芽孢杆菌中，葡萄糖通过与RNA聚合酶(RNAP)相关的CSHA(RNA解旋酶)的乙酰化来诱导细胞外Sigma因子基因sigX和Sigm的表达。我们对SigX-LacZ没有葡萄糖诱导(GI)的突变株进行了转座子突变筛选。在筛选此类突变体时，我们最近发现sigX/M的GI涉及YlxR，这是一种核相关蛋白(NAP)，调节包括代谢基因在内的近400个基因。研究表明，乙酰化的CSHA正向调节含有ylxR的操纵子的表达。在这里，我们报告了sigX的GI所需的yqfO或tsaD的额外突变。YqfO含有一个功能未知的泛保守结构域。YqfO和YlxR被发现调节含有tsaEBD操纵子的表达。LacZ融合突变分析揭示了YlxR富含腺嘌呤的顺式元件。TsaD是合成苏氨酰氨基甲酰腺苷(t(6)A)所需的TsaEBD酶的一种成分。T(6)tRNA的修饰在生命的三个领域中是普遍存在的。Western印迹分析表明，在葡萄糖存在的情况下，tsaD突变降低了丙酮酸脱氢酶复合体(PDHc)的亚单位--可溶性PdhA、PdhB和PdhD的水平。这导致了PDHc功能的严重缺陷，从而降低了细胞内乙酰辅酶A的浓度，这是PDHc的反应产物，也是CSHA乙酰化的可能来源。因此，我们讨论了一个建议的葡萄糖反应系统(GRS)，涉及自我加强的CSHA乙酰化。这种自我增强的途径可能有助于维持蛋白质乙酰化的乙酰辅酶A池。
Glucose is the most favorable carbon source for many bacteria, which have several glucose-responsive gene networks. Recently, we found that in Bacillus subtilis glucose induces the expression of the extracellular sigma factor genes sigX and sigM through the acetylation of CshA (RNA helicase), which associates with RNA polymerase (RNAP). We performed a transposon mutagenesis screen for mutants with no glucose induction (GI) of sigX-lacZ. While screening for such mutants, we recently found that the GI of sigX/M involves YlxR, a nucleoid-associated protein (NAP) that regulates nearly 400 genes, including metabolic genes. It has been shown that acetylated CshA positively regulates expression of ylxR-containing operon. Here, we report additional mutations in yqfO or tsaD required for the GI of sigX. YqfO contains a universally conserved domain with unknown function. YqfO and YlxR were found to regulate expression of the tsaEBD-containing operon. Mutational analysis using lacZ fusions revealed the adenine-rich cis-element for YlxR. TsaD is a component of the TsaEBD enzyme required for the synthesis of threonylcarbamoyl adenosine (t(6)A). The t(6)A modification of tRNA is universal across the three domains of life. Western blot analysis showed that the tsaD mutation in the presence of glucose reduced levels of soluble PdhA, PdhB, and PdhD, which are subunits of the pyruvate dehydrogenase complex (PDHc). This resulted in severely defective PDHc function and thus reduced concentrations of cellular acetyl-CoA, a reaction product of PDHc and plausible source for CshA acetylation. Thus, we discuss a suggested glucose-responsive system (GRS) involving self-reinforcing CshA acetylation. This self-reinforcing pathway may contribute to the maintenance of the acetyl-CoA pool for protein acetylation.