Ingham C J, Dennis J, Furneaux P A
School of Biological Sciences, Nottingham University, UK.
Mol Microbiol. 1999 Jan;31(2):651-63. doi: 10.1046/j.1365-2958.1999.01205.x.
The expression and activity of transcription termination factor Rho and the requirement for transcription elongation factors NusA and NusG was investigated in Bacillus subtilis. Rho was present at < 5% of the level found in Escherichia coli, but Rho factors from these two bacteria had similar properties as RNA-activated ATPases and in vitro termination of transcription on the lambda tR1 terminator. The B. subtilis rho gene was autoregulated at the level of transcription; autoregulation required sequences within the rho mRNA leader region and gene. To date, the B. subtilis rho is the only gene from a Gram-positive bacterium found to be regulated by Rho. Rho was not involved in bulk mRNA decay in B. subtilis. The E. coli elongation factors NusA and NusG target Rho, and the importance of these proteins in B. subtilis was examined by gene disruption. The B. subtilis NusG was inessential for both the viability and the autoregulation of Rho, whereas NusA was essential, and the requirement for NusA was independent of Rho. This contrasts with E. coli in which NusG is essential but NusA becomes dispensable if Rho terminates transcription less efficiently.
对枯草芽孢杆菌中转录终止因子Rho的表达与活性以及转录延伸因子NusA和NusG的需求进行了研究。Rho的含量低于在大肠杆菌中发现的水平的5%，但来自这两种细菌的Rho因子作为RNA激活的ATP酶以及在λtR1终止子上的体外转录终止具有相似的特性。枯草芽孢杆菌的rho基因在转录水平上进行自我调节；自我调节需要rho mRNA前导区和基因内的序列。迄今为止，枯草芽孢杆菌的rho是发现受Rho调节的唯一来自革兰氏阳性细菌的基因。Rho不参与枯草芽孢杆菌中大量mRNA的降解。大肠杆菌的延伸因子NusA和NusG作用于Rho，通过基因破坏研究了这些蛋白质在枯草芽孢杆菌中的重要性。枯草芽孢杆菌的NusG对Rho的生存能力和自我调节都不是必需的，而NusA是必需的，对NusA的需求独立于Rho。这与大肠杆菌形成对比，在大肠杆菌中NusG是必需的，但如果Rho终止转录的效率较低，NusA就变得可有可无。
