<Tr> <Th> PubMed </Th> <Td> articles </Td> </Tr> <Tr> <Th> NCBI </Th> <Td> proteins </Td> </Tr> <P> RNA polymerase (ribonucleic acid polymerase), both abbreviated RNAP or RNApol, official name DNA - directed RNA polymerase, is a member of a family of enzymes that are essential to life: they are found in all organisms (- species) and many viruses . RNAP locally opens the double - stranded DNA (usually about four turns of the double helix) so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA, a process called transcription . A transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region before RNAP can initiate the DNA unwinding at that position . RNAP has intrinsic helicase activity, therefore no separate enzyme is needed to unwind the DNA (in contrast to DNA polymerase). RNAP not only initiates RNA transcription, it also guides the nucleotides into position, facilitates attachment and elongation, has intrinsic proofreading and replacement capabilities, and termination recognition capability . In eukaryotes, RNAP can build chains as long as 2.4 million nucleotides . </P> <P> RNAP produces RNA that functionally is either coding (for protein) (messenger RNA) (mRNA); or non-coding: so - called "RNA genes". At least four functional types of RNA genes exist: Transfer RNA (tRNA) - transfers specific amino acids to growing polypeptide chains at the ribosomal site of protein synthesis during translation; Ribosomal RNA (rRNA) - is a component of ribosomes; micro RNA (miRNA) - regulates gene activity; and catalytic RNA (Ribozyme)) - an enzymatically active RNA molecule . </P>

What role does rna polymerase play in transcription