When transcription factors attach to the DNA strand - How do they know in which direction they have to initialize the transcription by rna polymerase? Is it always read in the same direction anyway? What about those 'promoters'? Do they influence the transcription direction?
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asked Apr 22, 2014 at 15:39
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$\begingroup$ Do you mean by direction which of the two DNA strands is transcribed? Or do you mean whether the polymerase goes from 5' to 3', or from 3' to 5' on a single strand? $\endgroup$– Mad Scientist - on strikeApr 22, 2014 at 16:12
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1$\begingroup$ @MadScientist Although the first question is also interesting, the second one is the one which I am interested in at the moment. $\endgroup$– SprechblaseningenieurApr 22, 2014 at 18:45
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1 Answer
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Transcription always proceeds in the direction 5' (5-prime) to 3' (3-prime) on the coding strand of DNA. Binding of both transcription factors and RNA polymerase to DNA depends on sequence motifs in the DNA. Transcription always happens in the same direction with respect to the chemical structure of the coding DNA strand, while the transcription direction with respect to the structure of the chromosome depends on which strand the coding sequence is found on (and thus which strand is defined as the coding strand for that gene).
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2$\begingroup$ Just to clarify, RNAP moves relative to the template strand from 3' to 5'. The transcript is polymerized from 5' to 3' and has the same sequence as the coding strand (except U instead of T). $\endgroup$ Apr 22, 2014 at 18:52
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$\begingroup$ Thanks, good point. The whole process is described, with figures, in an NCBI online book here: ncbi.nlm.nih.gov/books/NBK22085 $\endgroup$– jarlemagApr 22, 2014 at 19:10
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$\begingroup$ Glad to hear that. You can also communicate that an answer is useful by clicking the checkmark next to the answer, "accepting" it. $\endgroup$– jarlemagApr 23, 2014 at 0:11
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$\begingroup$ I don't think transcription always goes $5' \rightarrow 3'$ wrt to coding strand. See en.wikipedia.org/wiki/… $\endgroup$ Jun 20, 2014 at 11:49
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$\begingroup$ In that instance there are two coding strands, so the transcription still goes the same way with respect to each coding strand. $\endgroup$– jarlemagJun 20, 2014 at 14:01