Transcription: Advanced Look --> 3.) Elongation

Elongation is the stage of transcription in which the Poll II complex creates a complementary strand of mRNA. Once the entire transcription unit has been 'copied', the Poll II must release the newly finished strand of mRNA. The general transcription factors involved in the process also release during or at the end of this stage of transcription. Clicking on each of the thumbnail images will bring up a larger, labeled version of the described scene.

To see the Quicktime movie for the following sequence of images, click here.

	Once the ATP have been added, an 'eye' opens in the DNA giving access to the DNA template, and the creation of mRNA can begin.
	Once mRNA elongation begins, TFIIE (olive green) and TFIIH (red) are released. Also released at this time are TFIIA and TFIIB (not shown).
	TFIIE is shown moving into the distance, and the mRNA strand is elongating rapidly.
	Elongation of the mRNA stops when the end of the transcription unit is reached.
	As elongation stops, the DNA 'eye' closes.
	The Poll II complex is now released from the DNA, along with the phosphates added to it by the ATP.
	As the Poll II comples dissociates from the DNA, the mRNA strand is released. At this time, TFIID also unbinds from the DNA, allowing the DNA to return to its normal shape.
	Transcription is now complete. An mRNA copy has been produced and is now ready to be moved outside of the nucleus and be used in the translation process.