Zhang A, Rimsky S, Reaban M E, Buc H, Belfort M
Molecular Genetics Program, New York State Department of Health and School of Public Health, Albany 12201-2002, USA.
EMBO J. 1996 Mar 15;15(6):1340-9.
Expression of the Escherichia coli StpA protein was investigated and a functional comparison undertaken with the structurally analogous nucleoid protein H-NS. Analysis of stpA and hns expression indicated that although stpA transcript levels are much lower than those of hns, the two gene products are capable of both negative autogenous control and cross-regulation. Examination of cellular proteins in stpA, hns, or stpA-hns backgrounds revealed that StpA can repress and activate a subset of H-NS-regulated genes. Mechanistic parallels in regulation of gene expression are indicated by the ability of both proteins to inhibit transcription from promoters containing curved DNA sequences, and to form nucleoprotein structures that constrain DNA supercoils. Despite their functional similarities, each molecule is capable of independent activities. Thus, H-NS regulates a class of genes that are unaffected by StpA in vivo, whereas StpA has much stronger RNA chaperone activity in vitro. We therefore propose that in addition to its role as a molecular back-up of H-NS, StpA's superior effect on RNA may be exploited under some specific cellular conditions to promote differential gene expression.
对大肠杆菌StpA蛋白的表达进行了研究，并与结构类似的类核蛋白H-NS进行了功能比较。对stpA和hns表达的分析表明，尽管stpA转录水平远低于hns，但这两种基因产物都能够进行负向自体调控和交叉调控。对stpA、hns或stpA-hns背景下的细胞蛋白进行检测发现，StpA能够抑制和激活一部分H-NS调控的基因。这两种蛋白都能够抑制含有弯曲DNA序列的启动子的转录，并形成限制DNA超螺旋的核蛋白结构，这表明它们在基因表达调控机制上存在相似之处。尽管它们功能相似，但每个分子都能够独立发挥作用。因此，H-NS调控一类在体内不受StpA影响的基因，而StpA在体外具有更强的RNA伴侣活性。我们因此提出，除了作为H-NS的分子备份作用外，在某些特定细胞条件下，StpA对RNA的卓越作用可能被用于促进差异基因表达。
