Roles of transcriptional and translational control mechanisms in regulation of ribosomal protein synthesis in Escherichia coli

ABSTRACTBacterial ribosome biogenesis is tightly regulated to match nutritional conditions and to prevent formation of defective ribosomal particles. InEscherichia coli, most ribosomal protein (r-protein) synthesis is coordinated with rRNA synthesis by a translational feedback mechanism: when r-proteins exceed rRNAs, specific r-proteins bind to their own mRNAs and inhibit expression of the operon. It was recently discovered that the second messenger nucleotide guanosine tetra and pentaphosphate (ppGpp), which directly regulates rRNA promoters, is also capable of regulating many r-protein promoters. To examine the relative contributions of the translational and transcriptional control mechanisms to the regulation of r-protein synthesis, we devised a reporter system that enabled us to genetically separate thecis-acting sequences responsible for the two mechanisms and to quantify their relative contributions to regulation under the same conditions. We show that the synthesis of r-proteins from the S20 and S10 operons is regulated by ppGpp following shifts in nutritional conditions, but most of the effect of ppGpp required the 5′ region of the r-protein mRNA containing the target site for translational feedback regulation and not the promoter. These results suggest that most regulation of the S20 and S10 operons by ppGpp following nutritional shifts is indirect and occurs in response to changes in rRNA synthesis. In contrast, we found that the promoters for the S20 operon were regulated during outgrowth, likely in response to increasing nucleoside triphosphate (NTP) levels. Thus, r-protein synthesis is dynamic, with different mechanisms acting at different times.IMPORTANCEBacterial cells have evolved complex and seemingly redundant strategies to regulate many high-energy-consuming processes. InE. coli, synthesis of ribosomal components is tightly regulated with respect to nutritional conditions by mechanisms that act at both the transcription and translation steps. In this work, we conclude that NTP and ppGpp concentrations can regulate synthesis of ribosomal proteins, but most of the effect of ppGpp is indirect as a consequence of translational feedback in response to changes in rRNA levels. Our results illustrate how effects of seemingly redundant regulatory mechanisms can be separated in time and that even when multiple mechanisms act concurrently their contributions are not necessarily equivalent.</jats:p

Foreign Direct Investment For Developing Financing: Teaching Market-Related Aspects Through Cases

This article presents two cases that have been used to supplement the teaching of how market-related aspects impact decisions, policies and tasks associated with attracting foreign direct investment into emerging markets and developing economies. The authors share their experiences in workshops and in the classroom and provide discussion strategies and teaching notes for each case

Knowledge, action, and the frame problem

AbstractThis paper proposes a method for handling the frame problem for knowledge-producing actions. An example of a knowledge-producing action is a sensing operation performed by a robot to determine whether or not there is an object of a particular shape within its grasp. The work is an extension of Reiter's approach to the frame problem for ordinary actions and Moore's work on knowledge and action. The properties of our specification are that knowledge-producing actions do not affect fluents other than the knowledge fluent, and actions that are not knowledge-producing only affect the knowledge fluent as appropriate. In addition, memory emerges as a side-effect: if something is known in a certain situation, it remains known at successor situations, unless something relevant has changed. Also, it will be shown that a form of regression examined by Reiter for reducing reasoning about future situations to reasoning about the initial situation now also applies to knowledge-producing actions

Limeboo: Lime as a Replacement for Cement in Wall-Framing Systems with Bamboo-Guadua (Bahareque Encementado)

Traditional construction systems with the bamboo species Guadua angustifolia Kunth (Guadua) are standardized under the Colombian code for seismic-resistant buildings '1'. These systems are regarded as highly environmentally friendly due to their intensive use of Guadua in the supporting structure and walls. In particular, the plastered cane building system or 'bahareque encementado', which provides a low-cost and low-technology alternative for two-storey dwellings, commonly uses round Guadua for the frame and riven Guadua boards (esterilla) for covering the frame. However, this wall-framing system relies heavily on cement renders for providing combined structural action to resist lateral loads, protecting the material against weathering and ensuring a flat surface for construction finishes. Thick cement renders contribute greatly to the wall mass and together with the foundations result on the highest negative environmental impact in traditional wallframing construction with Guadua. Therefore, the reduction of the use of cement or its complete replacement for alternative binders in the wall-framing 'bahareque' system is a key point for environmental improvement. Widely available materials such as lime, which have less energy intensive production-processes present an alternative to cement. Moreover, lime offers improved breathability within the building and behaves more elastically than cement. This paper explores the potential use of lime as a replacement for cement mortars in 'bahareque' systems and analyses Guadua's anatomical and chemical features when mixed with lime. The paper describes a 'cold process' in which no high temperatures are involved for the improvement of the bonding between lime and bamboo

Second Front

Illustration of soldiers marching; Photograph of Irving Siegelhttps://scholarsjunction.msstate.edu/cht-sheet-music/12164/thumbnail.jp

The Dilemma of Basia's Pendant: European Community Design and the Protection of an Artist's Creations and Intellectual Property

This article is a description of the process of protecting a designer’s intellectual property through registration with the European Union Intellectual Property Office or EUIPO or through relying on the status of an Unregistered Community Design. The article discusses the registration process as well as the process of invalidation and considers issues relating to the enforcement of rights. Finally, the article focuses on whether a complaint about possible copyright infringement may be lodged against an online retailer or an online e-commerce website that offers unlicensed sales or unauthorized copies of a designer’s design by utilizing the descriptions or photographs of the designer

A Primer On International Environmental Law: Sustainability As A Principle Of International Law And Custom

International environmental law draws from two important sources: international treaties and conventions\u27 and customary international law