[Abstract unavailable

No abstract

The control of mRNA stability is an important component of regulation in bacteria. Processing and degradation of mRNAs are initiated by an endonucleolytic attack, and the cleavage products are processively degraded by exoribonucleases. In many bacteria, these RNases, as well as RNA helicases and other proteins, are organized in a protein complex called the RNA degradosome. In Escherichia coli, the RNA degradosome is assembled around the essential endoribonuclease E. In Bacillus subtilis, the recently discovered essential endoribonuclease RNase Y is involved in the initiation of RNA degradation. Moreover, RNase Y interacts with other RNases, the RNA helicase CshA, and the glycolytic enzymes enolase and phosphofructokinase in a degradosome-like complex. In this work, we have studied the domain organization of RNase Y and the contribution of the domains to protein-protein interactions. We provide evidence for the physical interaction between RNase Y and the degradosome partners in vivo. We present experimental and bioinformatic data which indicate that the RNase Y contains significant regions of intrinsic disorder and discuss the possible functional implications of this finding. The localization of RNase Y in the membrane is essential both for the viability of B. subtilis and for all interactions that involve RNase Y. The results presented in this study provide novel evidence for the idea that RNase Y is the functional equivalent of RNase E, even though the two enzymes do not share any sequence similarity. mRNAs transmit the genetic information from DNA to proteins. In contrast to the high stability of tRNA and rRNA, bacterial mRNAs are readily degraded. This crucial feature ensures the ability of bacteria to respond quickly to changing environmental conditions by adding an extra layer of control, in addition to the regulation of transcription and enzymatic activities of proteins (1). Moreover, mRNA processing allows the adjustment of different expression levels for genes encoded in one operon, as observed for the ilv operon and the glycolytic gapA operon of the Gram-positive soil bacterium Bacillus subtilis (24,40,45).The enzymes that process and degrade RNAs are called RNases. In the two model organisms Escherichia coli and B. subtilis, a set of about 20 RNases has been described thus far, but only a small fraction of these are common to both bacteria (12). Some of these RNases (e.g., RNase M5 or RNase-Mini III in B. subtilis) are necessary for the maturation of one specific target, whereas others (e.g., RNase J1 or RNase Y in B. subtilis) are more promiscuous and have a more global impact on RNA metabolism (12, 43, 58). The individual RNases differ not only in their respective amino acid sequences and in their number of substrates but also in their enzymatic mode of action. Two different classes of RNases can be defined: exoribonucleases, which remove RNA nucleotides one at a time from either the 3Ј or the 5Ј end, and endoribonucleases, which cleave within the RNA molecule. For the degradation of mRNAs, the conc...

BackgroundMicroRNAs (miRNAs or miRs) participate in the regulation of several biological processes, including cell differentiation. Recently, miR-34a has been implicated in the differentiation of monocyte-derived dendritic cells, human erythroleukemia cells, and mouse embryonic stem cells. In addition, members of the miR-34 family have been identified as direct p53 targets. However, the function of miR-34a in the control of the differentiation program of specific neural cell types remains largely unknown. Here, we investigated the role of miR-34a in regulating mouse neural stem (NS) cell differentiation.Methodology/Principal FindingsmiR-34a overexpression increased postmitotic neurons and neurite elongation of mouse NS cells, whereas anti-miR-34a had the opposite effect. SIRT1 was identified as a target of miR-34a, which may mediate the effect of miR-34a on neurite elongation. In addition, acetylation of p53 (Lys 379) and p53-DNA binding activity were increased and cell death unchanged after miR-34a overexpression, thus reinforcing the role of p53 during neural differentiation. Interestingly, in conditions where SIRT1 was activated by pharmacologic treatment with resveratrol, miR-34a promoted astrocytic differentiation, through a SIRT1-independent mechanism.ConclusionsOur results provide new insight into the molecular mechanisms by which miR-34a modulates neural differentiation, suggesting that miR-34a is required for proper neuronal differentiation, in part, by targeting SIRT1 and modulating p53 activity.

Background: An epigenetic switch regulates biofilm formation. Results: Sequence-specific DNA binding by SinR has been visualized, and the macromolecular interactions in the epigenetic switch have been analyzed. Conclusion: DNA binding by SinR requires precise protein-DNA contacts and SinR-induced DNA deformation. Significance: The macromolecular interactions at the center of biofilm formation have been analyzed.