Chapter 17: Fatty Acid Metabolism: Oxidation, Ketone Bodies, and Biosynthesis

Section 17.1 explores regulation in bacteria, focusing on the lac operon as a model for inducible control and the trp operon as a model for repressible control. Key players such as repressors, activators, operators, and inducers are introduced, along with allosteric regulation and feedback inhibition. Attenuation mechanisms in amino acid biosynthesis operons are discussed as examples of transcription-translation coupling. Section 17.2 transitions to eukaryotic gene regulation, which operates at multiple levels: chromatin structure, transcription initiation, mRNA processing, translation, and post-translational modification. Chromatin remodeling via histone acetylation and methylation is emphasized, with enzymes like histone acetyltransferases (HATs) and deacetylases (HDACs) mediating access to DNA. Transcriptional control involves transcription factors, enhancers, silencers, and mediator complexes that link DNA-bound activators to RNA polymerase II. The importance of combinatorial control and transcription factor modularity is also addressed. Section 17.3 delves into post-transcriptional regulation, including alternative splicing, RNA editing, mRNA localization, and RNA stability. Section 17.4 focuses on translational control, such as upstream open reading frames (uORFs), internal ribosome entry sites (IRES), and global regulation via eIF2α phosphorylation in response to stress. Section 17.5 highlights the role of small noncoding RNAs (e.g., microRNAs and siRNAs) in gene silencing, and the RNA interference (RNAi) pathway is explored in detail. Section 17.6 reviews regulation by protein degradation, such as ubiquitin tagging and proteasome-mediated turnover, connecting gene expression to protein half-life and cellular response. The chapter concludes by linking gene regulation to development, cell identity, disease, and biotechnology applications, emphasizing the intricacy and adaptability of gene expression networks.