VCAC: Molecular Processes: mRNA Processing: Advanced Look: Cleavage

Questions? Comments? Please contact Dr. Phillip McClean or Christina Johnson.

Flythrough Tour

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CELLULAR PROCESSES

Atp Synthase

Electron Transport Chain

Protein Trafficking

Protein Modification

Protein Recycling

Insulin Signaling

Constitutive Secretion

Regulated Secretion

Mitochondrial Protein Transport

Photosynthesis (Light)

Photosystem II

Mitosis

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MOLECULAR PROCESSES

Transcription

Regulated Transcription

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HOME > mRNA PROCESSING > ADVANCED LOOK > 1.) CAPPING > 2.) CLEAVAGE

mRNA Processing: Advanced Look --> 2.) Cleavage

The second major step in processing pre-mRNA is the removal of a portion of its 3' end. Clicking on each of the thumbnail images will bring up a larger, labeled version of the described scene.

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

	Certain signal sites control where the proteins required for cleavage and polyadenylation will attach. The upstream poly(A) signal is a specific sequence of nucleotides.
	The downstream poly(A) signal is not a specific sequence, rather it is a GU-rich region on the pre-mRNA.
	After transcription has been completed, the first two cleavage factors attach to the up and downstream poly(A) signal sites.
	These cleavage factors interact with each other to bring the signal sites into proximity with each other, forming a loop in the pre-mRNA.
	Two additional cleavage factors then attach and help to stabilize the complex.
	Poly(A) polymerase (PAP) then interacts with the complex and cleaves the strand of pre-mRNA at the poly(A) site.
	Once cleavage has occured, most of the cleavage factors are released.

NEXT --> 3.) POLYADENYLATION