Quisel J D, Grossman A D
Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
J Bacteriol. 2000 Jun;182(12):3446-51. doi: 10.1128/JB.182.12.3446-3451.2000.
Two chromosome partitioning proteins, Soj (ParA) and Spo0J (ParB), regulate the initiation of sporulation in Bacillus subtilis. In a spo0J null mutant, sporulation is inhibited by the action of Soj. Soj negatively regulates expression of several sporulation genes by binding to the promoter regions and inhibiting transcription. All of the genes known to be inhibited by Soj are also activated by the phosphorylated form of the transcription factor Spo0A (Spo0A approximately P). We found that, in a spo0J null mutant, Soj affected sporulation, in part, by decreasing the level of Spo0A protein. Soj negatively regulated transcription of spo0A and associated with the spo0A promoter region in vivo. Expression of spo0A from a heterologous promoter in a spo0J null mutant restored Spo0A levels and partly bypassed the sporulation and gene expression defects. Soj did not appear to significantly affect phosphorylation of Spo0A. Thus, in the absence of Spo0J, Soj inhibits sporulation and sporulation gene expression by inhibiting accumulation of the activator protein Spo0A and by acting downstream of Spo0A to inhibit gene expression directly.
两种染色体分配蛋白，Soj（ParA）和Spo0J（ParB），调节枯草芽孢杆菌中芽孢形成的起始。在spo0J基因缺失突变体中，芽孢形成受到Soj作用的抑制。Soj通过结合启动子区域并抑制转录，对几个芽孢形成基因的表达起负调控作用。所有已知受Soj抑制的基因也都被转录因子Spo0A的磷酸化形式（Spo0A~P）激活。我们发现，在spo0J基因缺失突变体中，Soj部分地通过降低Spo0A蛋白水平来影响芽孢形成。Soj对spo0A的转录起负调控作用，并在体内与spo0A启动子区域结合。在spo0J基因缺失突变体中，从异源启动子表达spo0A可恢复Spo0A水平，并部分绕过芽孢形成和基因表达缺陷。Soj似乎并未显著影响Spo0A的磷酸化。因此，在没有Spo0J的情况下，Soj通过抑制激活蛋白Spo0A的积累以及在Spo0A下游直接作用抑制基因表达，来抑制芽孢形成和芽孢形成基因表达。
