Promotor transcription factors

Chicken ovalbumin, Upstream promotor transcription factor (COUP-TF) Heterodimer 7 Direct repeat... 

Fig. 3.6. Principles of signal transduction by transmembrane receptors and nuclear receptors, a) transmembrane receptors receive the signal on the cell surface and convert it into an intracellular signal that can be passed on until it reaches the nucleus, b) In signal transduction via nuclear receptors the hormone enters the cell and binds the receptor either in the cytosol (R) or nucleus (R ). Nuclear receptors act as nuclear transcription factors that bind specific DNA elements (HRE hormone responsive element) found in the promotor region of regulated genes to control their transcription rate.

Oral administration of exogenous compounds can induce tissue-specific expression of previously transfected (and integrated) genes and transcription factors. Such compounds typically cause conformational changes in the transcription/activating factors that in turn cause their binding to the promotor linked to the transgene. 

Prestridge, D. S. (1995) Predicting Pol II promotor sequences using transcription factor binding sites. J Mol Biol 249, 923-932. 

General transcription factors (GTFs) help to localize the RNA polymerase correctly on the promotor and to form a transcription-competent initiation complex. They serve to impose a specific structure on the transcription start site, and some of them are required for elongation of the transcript. 

Chromatin-modifying and chromatin-remodeling activities are required for establishing a transcription-competent status on chromatin-covered promotors. The proteins involved are found in multi-subunit assemblies of varying composition. Specific transcription factors and mediators communicate with the chromatin-modifying activities. 

Overall, the general transcription factors can be assigned the role fulfdled by a single protein in procaryotes - namely the cr-factor. This role includes the correct positioning of the RNA polymerase on the promotor and the preparation for the incorporation of the first nucleotide. The addition of ATP to the pre-initiation complex leads to a rapid melting of the promotor, initiation of RNA synthesis, and dissociation of the RNA polymerase from the promotor. 

RNA polymerase II can be isolated from the cell in various forms. From yeast and from metazooans, holoenzyme forms of RNA polymerase have been purified that are composed of the core of RNA polymerase II and other accessory transcription factors, suggesting that a preassembled transcription apparatus can be assembled at the promotor in one step. These holoenzymes are formed from the core of RNA polymerase associated to a variable degree with the general transcription factors and with one or more other subunit complexes called mediators or coactivators. 

Cooperative binding of architectural and regulatory proteins to binding sites of the enhancer creates a multiprotein-DNA complex named an enhanceosome, which is essential for the initial modifications of chromatin at promotors and for stable binding of the core transcription apparatus. Protein-induced DNA bending, histone modification, histone mobilization, and cooperative, combinatorial interactions between different transcription factors are major tools used in enhanceosome-mediated transcriptional regulation. 

Substrate recognition and selection of the JNK/SAPK and p38 proteins (and also the ERK proteins) are mediated both by specific docking sites and by the nature of the amino acids surrounding the phosphoacceptor site. For the transcription factor substrates, specific docking domains have been identified that are loacted at a distance from the phosphorylation sites in the transactivation domain. These docking sites serve to increase the selectivity and specificity of phosphorylation, and they are used for recruitment of MAPK kinases into protein complexes at promotors, where they can phosphorylate other regulatory transcriptional proteins. 

Kemmler, 1., Schreiber, E., Muller, M.M., Matthias, P. and Schaffner, W. (1989) Octamer transcription factor bind to two different sequence motifs of the immunoglobulin heavy chain promotor. EMBOJ. 8 2001-2008. 

Tlie nuclear respiratory factors (NRF-1 and NRF-2) are nuclear transcription factors tfiat bind to and activate promotor regions of the nuclear genes encoding subunits of the respiratory chain complexes, including cytochrome c. They also activate the transcription of the nuclear gene for the mitochondrial transcription factor (mTF)-A. The protein product of this gene translocates into the mitochondrial matrix, where it stimulates transcription and replication of the mitochondrial genome. 

Transcription initiation in procaryotes is controlled via promotors and regulatory DNA sequences located near the promotor. The role of the promotor is to provide a defined association site for the RNA polymerase and to correctly orient it. The binding of the RNA polymerase to its promotor is controlled by the sigma factor, a component of the RNA polymerase holoenzyme. The sigma factor selects which genes are to be transcribed by specifically recognizing the promotor sequence and structure and by allowing the RNA polymerase to form a transcription-competent complex at the transcription start site. 

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