How does a RNAP locate a specific gene? For instance, growth hormone has to be produced and the RNAP has to locate the gene. But the promoter (TATA box) will also be present infront of all cistrons. So how does the RNAP choose the specific gene? Are the promoters specific for specific gene?
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1$\begingroup$ Yes, promoters are specific to genes and there is much more to them than the TATA box. There is also a requirement for specific transcription factors. And there are regulatory regions independent of the promoter. $\endgroup$– canadianerCommented Jul 9, 2015 at 4:55
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$\begingroup$ How exactly RNAP find a gene quickly that it is like finding a needle in the haystack $\endgroup$– Naveen KumaarCommented Jul 9, 2015 at 5:06
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$\begingroup$ Diffusion. There are thousands of RNAPs in a single cell. Furthermore, it is thought that these polymerases are localized to discrete sites of high transcriptional activity within the nucleus. Also keep in mind that transcribing genes quickly isn't necessarily the objective of the cell. Rather, a cell seeks to transcribe genes at a specific rate (which could be slow or fast). $\endgroup$– canadianerCommented Jul 9, 2015 at 5:19
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1$\begingroup$ This question is actually quite relevant. There are many mechanisms that increase the rate of TF-DNA binding- molecular crowding and nuclear organization are some factors. I'll address this in a while. Have a presentation to make. $\endgroup$– WYSIWYGCommented Jul 9, 2015 at 9:11
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It could be difficult for RNApol to access genes inactivated because inactivated genes are often tightly packed by chromatin. Many genes have enhancer elements(specific DNA sequences) as well as TATA, and transcriptional enhancers, which are proteins, would recognize enhancer elements in a sequence dependent manner and loosen chromatin structure to make RNApol access TATA sequences easily. Transcriptional enhancers also bind to the General Transcriptional Factor complex (GTF), which contains RNApol, therefore enhancers could bring RNApol to TATA sequences. Many tissue specific and/or developmentally-regulated transcriptional enhancers are identified. You could say transcriptional enhancers regulate RNApol which to bind.
