Chromosome partitioning at the initiation of sporulation in Bacillus subtilis

染色体在枯草芽孢杆菌孢子形成起始阶段的分配机制目前研究较少，但它是一个与细胞分化和染色体复制有关的重要课题。孢子形成起始信号由磷酸中继系统感知，孢子形成由反应调节剂spoOA-P的积累启动。几种生物信号，如营养剥夺、DNA复制和分配、细胞分裂和细胞密度，被输入到磷酸中继系统并调节活性SpoOA的浓度。spoOJ操纵子（spoOJA-spoOJB）位于枯草B.subtilis染色体的复制起点附近。它是parA-parB操纵子的同源性，在质粒分配中起重要作用。roj基因位于spoOJ操纵子的上游，编码SpoOJB同源基因，本研究分析了这些基因的功能。我们发现（i）spoOJB是营养细胞染色体分配所必需的，（ii）SpoOJA蛋白抑制孢子形成起始（阶段I）的磷酸化和不对称分隔或染色体分配，（iii）SpoOJB蛋白抑制SpoOJA的功能;即SpoOJB通过SpoOJA参与孢子形成起始时的染色体分配。SpoOJB抑制磷酸化传递和染色体分配表明SpoOJA/SpoOJB协调这些机制。我们还分析了spoOJ操纵子的转录调控，发现Roj蛋白是spoOJ操纵子的阻遏物，并且spoOJ操纵子的表达在孢子形成起始时被SpoOA阻遏。

The mechanism of chromosome partitioning at the initiation of sporulation in Bacillus subtilis is so far not much studied, but it is a very important subject concerning the cellular differentiation and chromosome replication. Sporulation initiation signals are sensed by the phosphorelay system and the sporulation is initiated by the accumulation of the response regulator spoOA-P.Several environ-mental signals, such as nutrient deprivation, DNA replication and partitioning, cell division, and cell density, are input into the phosphorelay system and regulate the concentration of the active SpoOA.The spoOJ operon (spoOJA-spoOJB) is located near the replication origin of the B.subtilis chromosome. It is a homology of the parA-parB operon which plays an important role in the plasmid partitioning. The roj, which encodes a SpoOJB homolog, is located upstream of the spoOJ operon.In the present study we have analyzed the function of these genes. We found that (i) spoOJB is necessary for the chromosome partitioning of the vegetative cells, (ii) SpoOJA protein represses the phosphorelay and the asymmetric septation or chromosome partitioning at the initiation of sporulation (stage I), and (iii) SpoOJB protein represses the function of SpoOJA ; i.e.SpoOJB participates in the chromosome partitioning at the initiation of sporulation through SpoOJA.The fact that the SpoOJA/SpoOJB repress the phosphorelay and chromsome partitioning suggests that SpoOJA/SpoOJB coordinate these mechanisms. We also analyzed the transcriptional regulation of the spoOJ operon and found that Roj protein is a repressor of the spoOJ operon and the expression of the spoOJ operon is repressed by SpoOA at the initiation of sporulation.