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During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript. In virology, the term transcription is used when referring to mRNA synthesis from a viral RNA molecule.
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]
Bacterial transcription differs from eukaryotic transcription in several ways. In bacteria, transcription and translation can occur simultaneously in the cytoplasm of the cell, whereas in eukaryotes transcription occurs in the nucleus and translation occurs in the cytoplasm. [14]
All these steps involve a series of interactions to initiate and complete the transcription of DNA in the nucleus of eukaryotes. Certain factors play key roles in the activation and inhibition of transcription, where they regulate primary transcript production. Transcription produces primary transcripts that are further modified by several ...
Polyadenylation occurs during and/or immediately after transcription of DNA into RNA. After transcription has been terminated, the mRNA chain is cleaved through the action of an endonuclease complex associated with RNA polymerase. After the mRNA has been cleaved, around 250 adenosine residues are added to the free 3' end at the cleavage site.
A large part of gene regulation occurs through transcription factors that either recruit or inhibit the binding of the general transcription machinery and/or the polymerase. This can be accomplished through close interactions with core promoter elements, or through the long distance enhancer elements.
During translation, ribosomes synthesize polypeptide chains from mRNA template molecules. In eukaryotes, translation occurs in the cytoplasm of the cell, where the ribosomes are located either free floating or attached to the endoplasmic reticulum. In prokaryotes, which lack a nucleus, the processes of both transcription and translation occur ...
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.