Regulation of transcription of the Bacillus subtilis pyrG gene, encoding cytidine triphosphate synthetase.
Regulation of transcription of the Bacillus subtilis pyrG gene, encoding cytidine triphosphate synthetase.
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枯草芽孢杆菌pyrG 基因转录的调节，编码胞苷三磷酸合成酶。
DOI：
10.1128/jb.183.19.5513-5522.2001
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发表时间：
2001
影响因子：
3.2
通讯作者：
Switzer,RL
中科院分区：
文献类型：
--
作者：
Meng,Q;Switzer,RL
TheB. subtilis pyrGgene, which encodes CTP synthetase, is located far from the pyrimidine biosynthetic operon on the chromosome and is independently regulated. ThepyrGpromoter and 5′ leader were fused tolacZand integrated into the chromosomes of severalB. subtilisstrains having mutations in genes of pyrimidine biosynthesis and salvage. These mutations allowed the intracellular pools of cytidine and uridine nucleotides to be manipulated by the composition of the growth medium. These experiments indicated thatpyrGexpression is repressed by cytidine nucleotides but is largely independent of uridine nucleotides. The start ofpyrGtranscription was mapped by primer extension to a position 178 nucleotides upstream of the translation initiation codon. A factor-independent termination hairpin lying between thepyrGpromoter and its coding region is essential for regulation ofpyrGexpression. Primer-extended transcripts were equally abundant in repressed and derepressed cells when the primer bound upstream of the terminator, but they were much less abundant in repressed cells when the primer bound downstream of the terminator. Furthermore, deletion of the terminator frompyrG-lacZfusions integrated into the chromosome yielded elevated levels of expression that was not repressible by cytidine. We suggest that cytidine repression ofpyrGexpression is mediated by an antitermination mechanism in which antitermination by a putativetrans-acting protein is reduced by elevated levels of cytidine nucleotides. Conservation of sequences and secondary structural elements in thepyrG5′ leaders of several other gram-positive bacteria indicates that theirpyrGgenes are regulated by a similar mechanism.
