Will W Ryan, Navarre William W, Fang Ferric C
Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA.
Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
Curr Opin Microbiol. 2015 Feb;23:8-13. doi: 10.1016/j.mib.2014.10.005. Epub 2014 Nov 5.
Horizontal gene transfer is a major contributor to bacterial evolution and diversity. For a bacterial cell to utilize newly-acquired traits such as virulence and antibiotic resistance, new genes must be integrated into the existing regulatory circuitry to allow appropriate expression. Xenogeneic silencing of horizontally-acquired genes by H-NS or other nucleoid-associated proteins avoids adventitious expression and can be relieved by other DNA-binding counter-silencing proteins in an environmentally-responsive and physiologically-responsive manner. Biochemical and genetic analyses have recently demonstrated that counter-silencing can occur at a variety of promoter architectures, in contrast to classical transcriptional activation. Disruption of H-NS nucleoprotein filaments by DNA bending is a suggested mechanism by which silencing can be relieved. This review discusses recent advances in our understanding of the mechanisms and importance of xenogeneic silencing and counter-silencing in the successful integration of horizontally-acquired genes into regulatory networks.
水平基因转移是细菌进化和多样性的主要贡献因素。对于细菌细胞而言，要利用新获得的特性（如毒力和抗生素抗性），新基因必须整合到现有的调控回路中以实现适当表达。由H-NS或其他类核相关蛋白对水平获得基因进行的异源沉默可避免偶然表达，并且可被其他DNA结合反沉默蛋白以环境响应和生理响应的方式解除。生化和遗传学分析最近表明，与经典转录激活不同，反沉默可发生在多种启动子结构中。通过DNA弯曲破坏H-NS核蛋白丝是一种解除沉默的推测机制。本综述讨论了我们在理解异源沉默和反沉默在水平获得基因成功整合到调控网络中的机制和重要性方面的最新进展。
