MCB 121 Lecture 12

MCB 121 Lecture 12 - MCB 121 Lecture 12 MT 2(thus 2/18...

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MCB 121 - Lecture 12 MT 2 (thus 2/18), Review session: 6-8pm 1322 Storer Outline: I. Nuclear Hormone Receptor II. Other transcription reg. III. Summary of Reg. IV. Global analysis of Reg. ------------------------------------------ Nuclear Hormone Receptors: (~48 in humans) - a class of transcription factor - Ex. Glucocorticoid receptor = GR - cytosolic (in unbound form) - nuclear, dimerize, binds DNA directly, and activate genes (in bound form by hormone) - Ex. Thyroid hormone receptor - form heterodimer with "retinoid X receptor (RXR)" - always nuclear and always dimerize (independent of the binding of hormone) - always bind to DNA directly No hormone => * in the absence of hormone, heterodimer of RXR and TR associates with NcorR, sin3, and MRPD3 * MRPD3 = HDAC - removes acetyl group from histone => leads to closed chromatin and reduced gene expression * MRPD3 is the only protein here has activity. * NcoR & sin3 are co-repressor because they are the adaptor which attaches MRPD to (RXR + TR) ----------------------------- With hormone => * structure change ( conformational change ) in the receptor complex * RXR+TR remains bound on the TRE (or the binding is in equilibrium, it could be the same one that binds the hormone or new one) * binding of hormone (TH) causes the dissociation of NcoR + sin3 + MRPD3 and creates a space for different set of proteins: P300/CBP + P/CA+ TAFII250 ** these 3 proteins have HAT activity: acetylate histones which open the chromatin and activate gene expression.
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* * TAF II = TATA-binding protein associated factor = it's part of TFIID => so this complex not only has HAT activity, it also holds the TFIID in position so it can be put on the TATA box (more tightly bound) 1) acetylate histones 2) recruit basal apparatus TRE = the enhancer = binding site for regulatory factors. Nature of binding site can also cause confirmation change of the protein.
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MCB 121 Lecture 12 - MCB 121 Lecture 12 MT 2(thus 2/18...

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