What is mediator and what role does it play in Pol II transcription?
The Mediator complex is a multi-subunit assembly that appears to be required for regulating expression of most RNA polymerase II (pol II) transcripts, which include protein-coding and most non-coding RNA genes.
What genes does RNA polymerase II transcribe?
Key Points. RNA polymerase II (Pol II) transcribes all eukaryotic protein-coding genes and most non-coding RNA genes. The final step of transcription is termination, which leads to the release of Pol II and RNA from the DNA template through a poorly defined mechanism.
Does the mediator bind to RNA polymerase?
In addition to RNA polymerase II, mediator must also associate with transcription factors and DNA. The mediator functions as a coactivator and binds to the C-terminal domain of RNA polymerase II holoenzyme, acting as a bridge between this enzyme and transcription factors.
Is RNA polymerase II a transcription factor?
A minimal RNA polymerase II (pol II) transcription system comprises the polymerase and five general transcription factors (GTFs) TFIIB, -D, -E, -F, and -H. The addition of Mediator enables a response to regulatory factors. Following initiation, pol II alone is capable of RNA transcript elongation and of proofreading.
What does mediator mean?
A mediator is a person who mediates—helps to settle a dispute or create agreement when there is conflict between two or more people or groups by acting as an intermediary or go-between for those parties. The act or process of mediating is called mediation.
How many subunits does RNA polymerase II have?
12
RNA polymerase II (pol II), the enzyme responsible for all mRNA synthesis in eukaryotes, has been isolated in two forms, a 12-subunit “complete” enzyme and a 10-subunit “core.” The two additional subunits of the complete enzyme, Rpb4 and Rpb7, form a heterodimer and associate reversibly with core.
What is the mediator in transcription?
Mediator is a multiprotein complex that is required for gene transcription by RNA polymerase II. Multiple subunits of the complex show specificity in relaying information from signals and transcription factors to the RNA polymerase II machinery, thus enabling control of the expression of specific genes.
Is mediator involved in regulating the initiation stage of transcription or the elongation stage of transcription?
Although Mediator was initially found to play a critical role in regulation of the initiation of Pol II transcription, recent studies have brought to light an expanded role for Mediator at post-initiation stages of transcription.
What does Mediator mean?
Why is the Mediator complex only required for transcription in vivo but is dispensable in vitro?
Why is the mediator complex only required for transcription in vivo, but is dispensable in vitro? In vivo (life) DNA is in chromatin, you need the mediator complex to unwind compared to in vitro (in the glass) where DNA is linear and purified – does not require unwinding.