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Unformatted text preview: actor. a) It binds DNA as a dimer, which is formed by a domain containing a leucine zipper. b) It acts directly on the transcription initiation complex containing RNA polymerase. c) It can stimulate transcription after it is phosphorylated at serine 133. d) It has a CRE-specific DNA-binding domain. e) It was isolated by affinity chromatography on a CRE-linked column from nuclear extracts of cAMP-rich PC12 cells. 18) The following is true about the CREB-Binding Protein (CBP). a) It is a histone methyltransferase, which methylates histones. b) It binds to CREB, only when CREB is phosphorylated. c) It mediates repression, when it is not bound to CREB. d) It is a component of the chromatin remodeling complex B for repression. e) It acts in direct opposition to histone acetyltransferase (HAT) activity. 19) The following is not true about ligands for nuclear hormone receptors. a) They are lipid soluble and thus can pass through the plasma membrane and even the nuclear membrane to reach receptors in the cytoplasm or nucleus. b) They include steroid hormones, retinoids, thyroid hormones, and vitamin D. c) RU-486/Mifepristone is an inactive, competitive inhibitor of the progesterone receptor (progesterone antagonist) and thereby acts to block pregnancy. d) Androgens, such as testosterone are derived from cholesterol to create the steroid hormone. e) None of the above. 20) The following is NOT true about histones and the histone code. a) Distinctive modification of histones by phosphorylation, methylation and acetylation result in specific changes in chromatin structure that are either conducive or inhibitory to gene transcription. b) Acetylation of histones alone coincides with transcriptional activation while methylation alone coincides with gene silencing. c) The nucleosome core contains an octameric assembly of histones. d) DNA that is tightly packaged by histones into nucleosomes is transcriptionally repressed or silenced. e) None of the above. 21) The following steps do NOT participate in transcriptional controls by...
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- Fall '08