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Transcription is the process of copying a segment of DNA into RNA for the purpose of gene expression.Some segments of DNA are transcribed into RNA molecules that can encode proteins, called messenger RNA (mRNA).
Bacterial transcription is the process in which a segment of bacterial DNA is copied into a newly synthesized strand of messenger RNA (mRNA) with use of the enzyme RNA polymerase. The process occurs in three main steps: initiation, elongation, and termination; and the result is a strand of mRNA that is complementary to a single strand of DNA.
RNA Polymerase II Transcription: the process of transcript elongation facilitated by disassembly of nucleosomes. RNAP from T. aquaticus pictured during elongation. Portions of the enzyme were made transparent so as to make the path of RNA and DNA more clear. The magnesium ion (yellow) is located at the enzyme active site.
Eukaryotic transcription occurs within the nucleus where DNA is packaged into nucleosomes and higher order chromatin structures. The complexity of the eukaryotic genome necessitates a great variety and complexity of gene expression control. Eukaryotic transcription proceeds in three sequential stages: initiation, elongation, and termination. [1]
Initiation of transcription begins with the binding of the enzyme to a promoter sequence in the DNA (usually found "upstream" of a gene). The DNA double helix is unwound by the helicase activity of the enzyme. The enzyme then progresses along the template strand in the 3’ to 5’ direction, synthesizing a complementary RNA molecule with ...
The preinitiation complex (PIC) is a large complex of proteins that is necessary for the transcription of protein-coding genes in eukaryotes and archaea.The PIC helps position RNA polymerase II over gene transcription start sites, denatures the DNA, and positions the DNA in the RNA polymerase II active site for transcription.
A capping enzyme (CE) is an enzyme that catalyzes the attachment of the 5' cap to messenger RNA molecules that are in the process of being synthesized in the cell nucleus during the first stages of gene expression. The addition of the cap occurs co-transcriptionally, after the growing RNA molecule contains as little as 25 nucleotides.
TFs work alone or with other proteins in a complex, by promoting (as an activator), or blocking (as a repressor) the recruitment of RNA polymerase (the enzyme that performs the transcription of genetic information from DNA to RNA) to specific genes. [6] [7] [8]