MBB331_Week9-Fall-2011

University press transcription factor families

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Unformatted text preview: eceptors: 2 Glucocorticoid Cys2-Cys2 Zn fingers Cys – Amino acids on right side of first finger Amino used for DNA binding, regulates DNA specificity - swapping first fingers between steroid receptors changes response element recognition response – Amnio acids on left side of second Amnio finger used for dimerization finger • 2 glucocorticoid receptor monomers glucocorticoid dimerize upon DNA binding - each monomer contacts successive major groove at response element palindromic seq Lewin Genes VII 2000 Oxford University Press TRANSCRIPTION FACTOR FAMILIES: STEROID RECEPTORS STEROID RECEPTORS • mutagenesis studies have been done mutagenesis to define functional domains to • unlike other transcription factors can’t unlike separate DNA-binding and activation • C-terminal domains used for hormone C-terminal binding and regulate receptors in variety of ways variety • removal of glucocorticoid receptor Cterm domain ---> constitutive term transcription activity - an internal negative regulator whose repression released by steroid binding released • similar to what we saw for σ 7 0 in similar bacteria: in the absence of interaction with RNAP, the N-terminal domain of σ 7 0 prevents σ 7 0 from binding DNA Lewin Genes VII 2000 Oxford University Press TRANSCRIPTION FACTOR FAMILIES: STEROID RECEPTORS STEROID RECEPTORS • • • similar to operator-repressor similar interaction, each response element for steroid hormone receptors consists of 2 half sites, thus we get receptor binding as a dimer receptor response elements for a number of response different steroid receptors have same sequence in their half sites; specificity is conferred by spacing between sites between importance of spacing between half importance sites is demonstrated by finding that changing spacing in GRE from 3 bp to 4 bp disrupts proper receptor-DNA interaction receptor-DNA OPERATOR/REPRESSOR-BINDING SITES: COOPERATIVE BINDING SITES: • • • -Repressor highest affinity for OL1 & OR1 Repressor R1 -Cooperative binding: binding at site 1 Cooperative increases repressor affinity for site 2… when OL1-2 & OR1-2 bound by repressor, PL & R1-2 PR transcription blocked • each operator contains each three 17bp repressorthree binding sites with binding partial symmetry about central base pair central central bp divides each central site into 2 half-sites, which show similarity to consensus sequence each half-site binds each one monomer in repressor dimer repressor site 1 in each operator site has a 10X greater affinity for repressor than other sites than...
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This note was uploaded on 03/26/2014 for the course MBB 321 taught by Professor Davidson during the Spring '11 term at Simon Fraser.

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