Transcription (genetics)#Elongation

Elongation during transcription handling the process through which the majority of the genetic code -containing DNA strand to a mRNA copies. This is the last phase of transcription after the pre-initiation complex partially dissolved and the mRNA has received a 5'- cap structure. The transcript is about 10 to 30 bases in length at this time and the cap structure already now binds the cap-binding complex.

In the elongation phase of RNA polymerase II elongation complex part of which is formed by the addition of several proteins. The energy required for the elongation provides the elimination of pyrophosphate from the NTPs. As a result, the elongating moves on DNA double-strand along, to the point of termination is reached. Already before that simultaneously starts the splicing of introns interspersed with still mRNA.

The elongating is the starting point for the regulation of elongation, and they can both slowed down, as are also accelerated. An automatic pause is inserted each time also when the complex is again ( after passing through a Histonschleife ) in the vicinity of the promoter. These regular intervals appear to be important for coordinating the elongation.

Initiation of elongation

The beginning of the elongation process is indicated by the dissociation of the capping enzyme II of the polymerase However, before the main reaction is under the complete control of the elongation complex, it must be assembled. First, the A- subunit ( RPB1 ) is dephosphorylated at serines polymerase 2 and 5; by these catalyzed by the phosphatase reaction, the CTD pol II is able to bind the protein complex, and DSIF NELF. Together with the kinase complex P- TEFb to the early elongating is full, and with DSIF: NELF may cause a break in the elongation and P- TEFb to the contrary plays by phosphorylation of serine -2.

The full elongating consists of the early elongating and the TFIIS protein, the FACT complex, the elongation factor ELL, the Elongin complex and the transcription factor IIH.

Main reaction

The central reaction during elongation and already during initiation is the extension of the mRNA along the lines of the bound single-stranded DNA, this example of a U:

⇒ PPi

UTP is esterified with RNA, it creates an extended RNA.

Further Reading

  • Conaway, J / Conaway, R / Reactome: .. RNA polymerase II transcription elongation
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