The molecular architecture of the sar locus in Staphylococcus aureus
The molecular architecture of the sar locus in Staphylococcus aureus
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DOI：
10.1128/jb.178.15.4563-4570.1996
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发表时间：
1996-08-01
影响因子：
3.2
通讯作者：
Cheung, AL
中科院分区：
文献类型：
--
作者：
Bayer, MG;Heinrichs, JH;Cheung, AL
金黄色葡萄球菌中的全球调节因子sar控制着多种细胞壁和胞外蛋白的合成，其中许多是假定的毒力因子。RN6390菌株的sar基因座包含一个339个碱基的开放阅读框(SARA)和一个860个碱基的上游区域，对该基因座的转录分析显示有三个不同的转录本(分别命名为SARA、SARC和SARB)：0.58、0.84和1.15 kb。这三个转录本似乎都处于时间和生长周期相关的调控之下，其中SARA和SARB在对数早期最丰富，而SARC在稳定期晚期的浓度最高。通过引物延伸和改进的S1核酸酶保护分析对sar转录本5‘端的定位表明，转录是由三个独立的、间距较大的启动子启动的，三个sar转录本的3’端是相同的，转录终止发生在典型的原核生物PolyT终止信号的上游。对含有不同启动子和终止信号的质粒的sar突变克隆的Northern(RNA)分析表明，这三个启动子都可以产生单独的转录本，因此可能是作为独立启动子激活的。启动转录的多启动子系统具有保守的特征，可被同源的sigma(70)转录因子识别，也可被在一般应激反应中表达的那些转录因子识别。在两个远端启动子(P3和P2)的下游是两个可能编码短肽的区域。可以想象，这些短肽和SarA基因产物之间的翻译后合作发生，以调节sar相关功能。一个sar突变体与一个表达所有三个sar转录本的克隆的互补研究表明，该克隆能够将sar野生型表型恢复到sar突变体。
The global regulator sar in Staphylococcus aureus controls the synthesis of a variety of cell wall and extracellular proteins, many of which are putative virulence factors. The sar locus in strain RN6390 contains a 339-bp open reading frame (sarA) and an 860-bp upstream region, Transcriptional analyses of this Locus revealed three different transcripts of 0.58, 0.84, and 1.15 kb (designated sarA, sarC, and sarB, respectively). All three transcripts seemed to be under temporal, growth cycle-dependent regulation, with sarA and sarB being most abundant in early log phase and the sarC concentration being highest toward the late stationary phase. Mapping of the 5' ends of the sar transcripts by primer extension and modified S1 nuclease protection assays demonstrated that transcription is initiated from three separate, widely spaced promoters, The 3' ends of all three sar transcripts are identical, and transcriptional termination occurs upstream of a typical prokaryotic poly(T) termination signal. Northern (RNA) analysis of sar mutant clones containing plasmids that comprised various promoters and the termination signal revealed that individual transcripts can be generated from each of the three promoters, thus suggesting possible activation as independent promoters. The multipromoter system, from which transcription is initiated, bears conserved features for recognition by homologous sigma(70) transcription factors and also by those expressed in the general stress response. Downstream of the two distal promoters (P3 and P2) are two regions potentially encoding short peptides. It is conceivable that posttranslational cooperation between these short peptides and the sarA gene product occurs to modulate sar-related functions. Complementation studies of a sar mutant with a clone expressing all three sar transcripts showed that this clone was able to restore the sar wild-type phenotype to the sar mutant.