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RNA polymerase (purple) unwinding the DNA double helix. It uses one strand (darker orange) as a template to create the single-stranded messenger RNA (green). In molecular biology , RNA polymerase (abbreviated RNAP or RNApol ), or more specifically DNA-directed/dependent RNA polymerase ( DdRP ), is an enzyme that catalyzes the chemical reactions ...
The initiation of the transcription is a multistep sequential process that involves several mechanisms: promoter location, initial reversible binding of RNA polymerase, conformational changes in RNA polymerase, conformational changes in DNA, binding of nucleoside triphosphate (NTP) to the functional RNA polymerase-promoter complex, and ...
Common changes in nucleotide analogues. Nucleic acid analogues are used in molecular biology for several purposes: Investigation of possible scenarios of the origin of life: By testing different analogs, researchers try to answer the question of whether life's use of DNA and RNA was selected over time due to its advantages, or if they were chosen by arbitrary chance; [3]
Retroviruses encode an unusual DNA polymerase called reverse transcriptase, which is an RNA-dependent DNA polymerase (RdDp) that synthesizes DNA from a template of RNA. The reverse transcriptase family contain both DNA polymerase functionality and RNase H functionality, which degrades RNA base-paired to DNA. An example of a retrovirus is HIV. [14]
This is in contrast to typical DNA-dependent RNA polymerases, which all organisms use to catalyze the transcription of RNA from a DNA template. RdRp is an essential protein encoded in the genomes of most RNA-containing viruses that lack a DNA stage, [ 1 ] [ 2 ] including SARS-CoV-2 .
To begin transcribing a gene, the RNA polymerase binds to a sequence of DNA called a promoter and separates the DNA strands. It then copies the gene sequence into a messenger RNA transcript until it reaches a region of DNA called the terminator , where it halts and detaches from the DNA.
RNA is similar to DNA, except that RNA contains uracil, instead of thymine, which forms a base pair with adenine. An important region for the activity of gene repression and expression found in RNA is the 3' untranslated region. This is a region on the 3' terminus of RNA that will not be translated to protein but includes many regulatory regions.
These two components, RNA polymerase and sigma factor, when paired together, build RNA polymerase holoenzyme which is then in its active form and ready to bind to a promoter and initiate DNA transcription. [8] Once it binds to the DNA, RNA polymerase turns from a closed to an open complex, forming the transcription bubble.