23Gene Regulation in Eukaryotes.ppt

23Gene Regulation in Eukaryotes.ppt - BIO 325 Genetics...

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Unformatted text preview: BIO 325 Genetics Lectures 22 and 23 Gene Regulation in Eukaryotes Gene Regulation in Eukaryotes The molecular mechanisms that underlie gene regulation in eukaryotes bear many similarities to the ways that bacteria regulate their genes. As in prokaryotes, regulation in eukaryotes can occur at any step in the pathway of gene expression. Proteins that influence the ability of the RNA polymerase to transcribe a gene are called transcription factors. General transcription factors bind the RNA polymerase to the core promoter. Regulatory transcription factors regulate the rate of gene transcription. These proteins typically recognize cis regulatory elements that are similar to operators in bacteria. These regions are generally known as control elements or regulatory elements. Regulatory Transcription Factors Transcription factors that increase the rate of transcription are called activators, and the regulatory element DNA sequence they bind to is called an enhancer. Transcription factors that decrease the rate of transcription are called repressors, and the regulatory element DNA sequence they bind to is called a silencer. Regulatory Transcription Factors Most eukaryotic genes, particularly those found in multicellular species, are regulated by many factors; this phenomenon is called combinational control. Regulatory Transcription Factors Regulatory Transcription Factors At the level of transcription, the following are common factors that contribute to combinational control: One or more activator proteins may stimulate the ability of RNA polymerase to initiate transcription. One or more repressor proteins may inhibit the ability of RNA polymerase to initiate transcription. The function of activators and repressors may be modulated in a variety of ways; these include the binding of small effector molecules, protein-protein interactions, and covalent modifications. Regulatory Transcription Factors At the level of transcription, the following are common factors that contribute to combinational control: Activator proteins may promote the loosening of chromatin compaction in the chromosome where the gene is located, thereby making it easier for the gene to be recognized and transcribed by RNA polymerase. DNA methylation may inhibit transcription, either by preventing the binding of an activator protein or by recruiting proteins that cause the chromatin to become more compact. Regulatory Transcription Factors All five of these factors can contribute to the regulation of a single gene, or possibly only three or four will play a role. In most cases, transcriptional regulation is aimed at controlling the initiation of transcription at the promoter. Regulatory Transcription Factors There are different families of evolutionarily related transcription factors....
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23Gene Regulation in Eukaryotes.ppt - BIO 325 Genetics...

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