Gene Regulation in Eukaryotes

Gene Regulation in - Gene Regulation in Eukaryotes Introduction The molecular mechanisms that underlie gene regulation in eukaryotes bear many

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1 Gene Regulation in Eukaryotes Introduction 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 (Figure 15.1). Regulatory Transcription Factors General information 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. Transcription factors that increase the rate of transcription are called activators, and the regulatory element DNA sequence they bind to is called an enhancer (Figure 15.2a). Transcription factors that decrease the rate of transcription are called repressors, and the DNA sequence they bind to is called a silencer (Figure 15.2b). Most eukaryotic genes, particularly those found in multicellular species, are regulated by many factors; this phenomenon is called combinational control. 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.
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2 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. 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. Structural features of regulatory transcription factors allow them to bind to DNA. There are different families of evolutionarily related transcription factors. Molecular structure of transcription factor proteins that allows them to bind to DNA is an area of intense research. Domains are regions of transcription factors that have specific functions. For example, one domain may have a DNA-binding function, while another
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This note was uploaded on 02/27/2011 for the course BIO 325 taught by Professor Saxena during the Spring '08 term at University of Texas at Austin.

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Gene Regulation in - Gene Regulation in Eukaryotes Introduction The molecular mechanisms that underlie gene regulation in eukaryotes bear many

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