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23Gene Regulation in Eukaryotes

23Gene Regulation in Eukaryotes - Gene Regulation in...

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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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