Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101.
Department of Biochemistry and Molecular Biology, University of Miami Miller School of Medicine, Miami, Florida 33101
J Biol Chem. 2019 Dec 27;294(52):19997-20008. doi: 10.1074/jbc.RA119.011367. Epub 2019 Nov 19.
RNase BN, the RNase Z family member, plays a limited role in tRNA metabolism, in contrast to most other organisms. However, RNase BN does act on 6S RNA, the global transcription regulator, degrading it in exponential-phase cells and maintaining it at low levels during this phase of growth. RNase BN levels decrease in stationary-phase cells, leading to elevation of 6S RNA and subsequent regulation of RNA polymerase. These findings were the first indication that RNase BN itself is growth phase-regulated. Here, we analyze the mechanism of this regulation of RNase BN. We find that RNase BN decreases in stationary phase because its mRNA becomes unstable, due primarily to its degradation by RNase E. However, in exponential-phase cells mRNA is stabilized due to binding by the sRNA, GcvB, and the protein, Hfq, which reduce cleavage by RNase E. Because the amount of GcvB decreases in stationary phase, mRNA is less protected and becomes increasingly unstable resulting in reduction in the amount of RNase BN. The small RNA-dependent, positive regulation of RNase BN in exponential-phase cells is the first example of this novel mechanism for RNase regulation.
RNase BN，属于 RNase Z 家族成员，在 tRNA 代谢中作用有限，这与大多数其他生物不同。然而，RNase BN 确实作用于 6S RNA，作为全局转录调节剂，在指数生长期的细胞中降解它，并在生长的这个阶段将其维持在低水平。RNase BN 的水平在静止期细胞中下降，导致 6S RNA 的升高，并随后调节 RNA 聚合酶。这些发现首次表明 RNase BN 本身是受生长阶段调控的。在这里，我们分析了这种 RNase BN 调控的机制。我们发现，由于其 mRNA 主要通过 RNase E 的降解而变得不稳定，因此在静止期 RNase BN 减少。然而，在指数生长期细胞中，mRNA 由于 sRNA GcvB 和蛋白 Hfq 的结合而稳定，这减少了 RNase E 的切割。由于 GcvB 在静止期的量减少，mRNA 受到的保护较少，变得越来越不稳定，导致 RNase BN 的量减少。在指数生长期细胞中，依赖于小 RNA 的 RNase BN 的正向调节是这种新型 RNase 调控机制的第一个例子。
