Transcriptional regulation is a term used to describe a number of biological processes by which transcription, the process through which the genetic data stored in DNA is transcribed to RNA, is controlled. Transcription is one of the major steps in the central dogma of biology that describes the overall process by which genes are expressed. The raw genetic data is contained in double stranded DNA, but it is mixed with a great deal of irrelevant data. Through transcription, the data contained in the double-stranded DNA is transcribed to a single-stranded RNA molecule and the irrelevant data is spliced out. Translation, the final major step, occurs when RNA transcripts are used to produce proteins, the final units of gene expression which serve countless functions within every organism.
Regulation of gene expression can occur at every level of the central dogma of biology. Transcriptional regulation is a specific form of gene regulation that occurs during the transcription process by moderating the rate of transcription. Sometimes this involves halting transcription entirely to stop the expression of a particular gene, while other times it may mean activating transcription in order to activate genes that are only used during certain environmental conditions. Transcriptional regulation is effective because it is the first major step of gene expression. It requires significantly less use of biological resources than regulation by preventing translation or regulation that affects the performance of already-translated proteins.
Transcriptional regulation is incredibly important to maintaining the health of an organism and involves many different factors. There is, for example, a temporal factor to transcriptional regulation; it is often important for proteins to be produced at a particular rate to maintain various important biological functions. Likewise, a response to environmental factors may require transcription to be quickly initiated. It is also important to make sure transcription occurs to an appropriate extent; if too many or too few proteins are produced, important equilibriums within the body may be adversely affected.
There are many different mechanisms of transcriptional regulation. Repressors and enhancers, for instance, are specialized molecules that either inhibit or enhance a protein's ability to bind to a promoter site on DNA in order to initiate transcription. Transcription factors are necessary to position RNA polymerase, the protein that is responsible for RNA synthesis, at an appropriate site on a DNA strand for transcription initiation. A higher concentration of a given transcription factor, then, could result in a higher rate of transcription.