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In genetics, a transcription terminator is a section of nucleic acid sequence that marks the end of a gene or operon in genomic DNA during transcription.This sequence mediates transcriptional termination by providing signals in the newly synthesized transcript RNA that trigger processes which release the transcript RNA from the transcriptional complex.
Termination of transcription occurs in the ribosomal intergenic spacer region that contains several transcription termination sites upstream of a Pol I pausing site. Through a yet unknown mechanism, the 3’-end of the transcript is cleaved, generating a large primary rRNA molecule that is further processed into the mature 18S, 5.8S and 28S rRNAs.
Transcription begins at the promoter when RNA polymerase, an enzyme that facilitates transcription of DNA into mRNA, binds to a promoter, unwinds the helical structure of the DNA, and uses the single-stranded DNA as a template to synthesize RNA. [1] Once RNA polymerase reaches the termination signal, transcription is terminated. [1]
RNA polymerase, assisted by one or more general transcription factors, then selects a transcription start site in the transcription bubble, binds to an initiating NTP and an extending NTP (or a short RNA primer and an extending NTP) complementary to the transcription start site sequence, and catalyzes bond formation to yield an initial RNA product.
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[33] [34] CPSF is in contact with RNA polymerase II, allowing it to signal the polymerase to terminate transcription. [35] [36] When RNA polymerase II reaches a "termination sequence" (⁵'TTTATT 3 ' on the DNA template and ⁵'AAUAAA 3 ' on the primary transcript), the end of transcription is signaled. [37]
Translation promotes transcription elongation and regulates transcription termination. Functional coupling between transcription and translation is caused by direct physical interactions between the ribosome and RNA polymerase ("expressome complex"), ribosome-dependent changes to nascent mRNA secondary structure which affect RNA polymerase activity (e.g. "attenuation"), and ribosome-dependent ...
Termination of elongation depends on eukaryotic release factors. The process is similar to that of bacterial termination, but unlike bacterial termination, there is a universal release factor, eRF1, that recognizes all three stop codons. Upon termination, the ribosome is disassembled and the completed polypeptide is released. eRF3 is a ribosome ...