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Initiation step of transcription is simply binding of RNA polymerase on the DNA strand and its activation by addition of a phosphate group onto it.

Different kind of promotors are present close to the transcription starting site and different kind of transcription factors (TFIID ,TFIIB ...) are present binding onto promotors making the RNA polymerase bind onto DNA.

is there different types of RNA polymerase II ? I know that it is RNA Polymerase II which is responsible for mRNA formation but my question is; is RNA Polymerase II further subdivided according to what kind of protein will be synthesised after translation? otherwise why do different kinds of transcription factors exist?

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  • $\begingroup$ Why didn't you research RNA polymerases before posting? This would have answered your question and saved you wasting other people's time. $\endgroup$ – David Jun 18 '18 at 18:53
  • $\begingroup$ "RNA Polymerase II which is responsible for mRNA formation but my question is; is RNA Polymerase II further subdivided according to what kind of protein will be synthesised after translation" shows clearly that ı researched about the subject and I am asking for a further detail that ı am NOT ABLE TO find an answer for. It is optional for one to share knowledge or not I think, so I am not wasting anyone's time I think. Your use of language is harsh and irritating. $\endgroup$ – Taylan Jun 18 '18 at 19:14
  • $\begingroup$ Please read "how to ask a good question" in the Help. You are required to do research before posting. There are ample articles on Wikipedia and elsewhere that describe the RNA polymerases and transcription factors in eukaryotes, as there are text book chapters in reputable books on biochemistry on NCBI Bookshelf. You cannot find anything about the mistaken idea you have about multiple RNA polymerases for the simple reason it is a misconception. The subject of tissue-specific or stimulus-specific transcription is huge — go read about it. $\endgroup$ – David Jun 18 '18 at 20:41
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TFs, the DNA they bind to, and the transcriptional machinery (including the Pol II [RNA polymerase 2] enzyme all form a complicated three-dimensional complex. It depends on the topographic conformation of the DNA, epigenetic factors, a whole bunch of things which are orchestrated. However, once the machinery is activated, the Pol II enzyme is capable of transcribing the DNA regardless of its resulting protein. You can get the enzyme to transcribe nonsense, or functional coding regions which will produce functional proteins.

In epigenomics, it is also commonplace to identify mRNA being transcribed on DNA regions which do not bind a transcription factor. This is because the machinery recruits the polymerase at a transcription initiation site, but there may be nearby DNA (looped, for instance, or on a neighboring nucleosome) which is accidentally transcribed, simply because the polymerase was brought into close proximity and began transcribing the wrong DNA.

Such enzyme reactions are a bit like chopping an onion: the knife is the enzyme, the onion is the target DNA, and your stray finger is the non-target DNA. Usually it is the onion that is chopped.

Biology is never perfect, it follows the laws of chemistry and therefore is a stochastic process.

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