Biol Chapt13

Biol Chapt13 - 13 Regulation of Cellular Processes CHAPTER...

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13 Regulation of Cellular Processes CHAPTER OVERVIEW This chapter considers a variety of mechanisms by which gene expression is regulated. The discussion begins by giving the levels of regulation of gene expression. The regulation of transcription initiation includes induction and repression using the lac , trp , and ara operons as examples, and includes two- component regulatory systems. Regulation at the level of transcription continues with attenuation and riboswitches. Translational and posttranslational regulation are discussed. Global regulatory systems include discussions of sigma factors, catabolite repression, chemotaxis, quorum sensing, and sporulation. The chapter concludes with information about gene regulation in eukaryotes and archaea. CHAPTER OBJECTIVES After reading this chapter you should be able to: discuss levels of regulation of gene expression describe induction and repression using example operons discuss regulation of enzyme synthesis by negative and positive regulatory proteins describe two-component regulatory systems describe attenuation and riboswitches discuss translational and posttranslational regulation discuss global regulation of gene expression describe quorum sensing and catabolite repression contrast regulation in eukaryotes, bacteria, and archaea CHAPTER OUTLINE I.Levels of Regulation A. Regulation of gene expression (controlling enzyme synthesis) occurs at different levels, including control of transcription, translation, and posttranslation B. Although there are similarities in the regulation of gene expression in organisms from different domains, there are many differences in chromosome organization, mRNA transcripts, signaling, and cell structure II.Regulation of Transcription Initiation A. Induction and repression of enzyme synthesis 1. Enzymes central to metabolic processes, routinely needed by cells, are encoded by housekeeping genes; these are constitutive genes that are continuously expressed 2. Synthesis of enzymes involved in catabolic pathways are often inducible and are only expressed when needed; the initial substrate of the pathway (or some derivative of it) is usually the inducer; induction increases the amount of mRNA encoding the enzymes 3. Synthesis of enzymes involved in anabolic pathways is often repressible and expressed when biosynthesis of the end product is needed; the end product of the pathway usually acts as a corepressor; repression decreases the amount of mRNA encoding the enzymes B. Control of transcription initiation by regulatory proteins 1. Regulatory proteins in bacteria contain recognizable DNA-binding domains such as zinc fingers and helix-turn-helix domains 2. Negative transcriptional control occurs when a repressor protein inhibits initiation of transcription; positive transcriptional control occurs when activator protein promotes initiation of transcription 131
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3. Even in operons where expression is repressed, a low basal level of transcription occurs;
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This note was uploaded on 05/02/2011 for the course BIOL 2051 taught by Professor Brininstool during the Spring '07 term at LSU.

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Biol Chapt13 - 13 Regulation of Cellular Processes CHAPTER...

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