Gene Expression - Lecture 3 "Repressible Operons & Attenuation Mechanisms" скачать в хорошем качестве

Gene Expression - Lecture 3 "Repressible Operons & Attenuation Mechanisms"

Welcome to Lecture 3: Regulation of Gene Expression in Bacteria (Repressible Operons) — an advanced exploration of how bacterial cells fine-tune gene expression when end-products are abundant, ensuring metabolic efficiency and precise control. In this lecture, we examine repressible gene systems using the tryptophan (trp) operon as a central model, and expand beyond protein-based regulation to include RNA-mediated mechanisms such as attenuation, riboswitches, and ribozymes. These regulatory strategies highlight how bacteria integrate transcriptional and translational processes to rapidly respond to intracellular metabolite levels. By the end of this video, you will understand how bacteria employ layered regulatory mechanisms to prevent unnecessary biosynthesis and maintain metabolic balance. In this lecture, you will learn: • Repressible Operons in Bacteria: The fundamental concept of repressible gene systems, where transcription is normally active and is shut down when the end product of a biosynthetic pathway accumulates. • The trp Operon Model: Structural and regulatory organization of the tryptophan operon, including the trpE, trpD, trpC, trpB, and trpA genes, and the role of the trpR regulatory gene. • Corepressor-Dependent Repression: How tryptophan acts as a corepressor by binding the aporepressor, inducing an allosteric conformational change that enables operator binding and transcriptional repression. • Attenuation as a Second Regulatory Layer: The mechanism of attenuation mediated by the leader sequence and alternative RNA secondary structures, allowing gene expression to respond sensitively to intracellular tryptophan levels. • Coupling of Transcription and Translation: How ribosome movement and charged tRNATrp availability determine whether transcription proceeds or terminates prematurely. • RNA Secondary Structure Control: The formation of terminator and antiterminator hairpins within the 5′ untranslated region and their direct impact on transcriptional outcomes. • Riboswitches: Regulation through metabolite-binding RNA elements that control transcription termination or translation initiation without the need for regulatory proteins. • Metabolite-Sensing Examples: Thiamin pyrophosphate (TPP) riboswitches as a model for ligand-dependent RNA conformational changes. • Ribozymes in Gene Regulation: Self-cleaving mRNA elements, such as the glmS ribozyme, that directly inhibit translation in response to metabolite accumulation. This lecture completes the framework of bacterial gene regulation by demonstrating how protein-based and RNA-based mechanisms work together to achieve highly efficient and responsive control of gene expression, preparing you for more advanced regulatory systems discussed in upcoming lectures. A very important note: The content and PDF materials featured in this presentation were created by the course professor, to whom all credit for the excellent preparation goes. I am sharing my lecture based on these materials. ملاحظة هامة: المحتوى والمواد الـ (PDF) المعروضة في هذا الفيديو هي من إعداد دكتور المادة، وله كل الشكر والفضل على المجهود الرائع في تحضيرها. #BUC #badruniversityincairo #biotechnology #transcriptomics #genetics #geneexpression #biology #university #buc