Promoter initiation of transcription

Transcription is catalyzed by DNA-dependent RNA polymerases, which use ribonucleoside 5 -triphosphates to synthesize RNA complementary to the template strand of duplex DNA. Transcription occurs in several phases binding of RNA polymerase to a DNA site called a promoter, initiation of transcript synthesis, elongation, and termination. 

As already noted, eukaryotic RNA polymerases have little or no intrinsic affinity for their promoters initiation of transcription is almost always dependent on the action of multiple activator proteins. One important reason for the apparent predominance of positive regulation seems obvious the storage of DNA within chromatin effectively renders most promoters inaccessible, so genes are normally silent in the absence of other regulation. The structure of chromatin affects access to some promoters more than others, but repressors that... 

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See also in sourсe #XX -- [ , , ]

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