Lecture 5 RNA Processing (Capping and Polyadenylation and the Regulation of mRNA Stability)

Lecture 5 RNA Processing (Capping and Polyadenylation and the Regulation of mRNA Stability)

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Unformatted text preview: IPHY 3060 Lecture 5: RNA Processing I Capping and Polyadenylation and the Regulation of mRNA Stability Key points from before A gene is a sequence of DNA that produces an RNA, which contains the information necessary to make a protein Transcription produces an RNA copy of a DNA sequence Key Point #1: After transcription, RNA requires additional processing before it can be used to create a protein 3 Main Types of RNA processing 5 Capping 3 Polyadenylation RNA Splicing All these steps occur in the nucleus, and only fully processed RNAs are exported into the cytoplasm to produce a protein 5 Capping and 3 Polyadenylation Main Function of 5 Capping and 3 Polyadenylation: Increase mRNA stability/decrease mRNA degradation The Central Dogma of Biology Information storage Information transfer Function The Central Dogma of Biology Information storage Information transfer Function RNA degradation The Central Dogma of Biology Information storage Information transfer Function The amount of RNA depends on both RNA synthesis (transcription) and RNA degradation RNA degradation Functions of mRNA Degradation Eliminates mutated or altered RNAs Eliminates improperly spliced or processed mRNAs Cellular defense against RNA viruses Along with transcription, regulates the total amount of mRNA available to produce a protein Key point: transcribed mRNAs contain leader sequences called untranslated regions or UTRs on either end that dont code for protein and which are important for RNA processing Transcription start site Transcription end site DNA mRNA ATG Translation start site Translation termination site TAG, TGA, TAA Protein 5 UTR 3 UTR The UTRs contain sequences important for 5 capping and 3 polyadenlyation RNAs are degraded by ribonucleases enzymes that degrade RNA Endoribonuclease attacks RNA in middle Exoribonuclease attacks at either end2 types:-5 to 3 exoribonuclease- starts at 5 UTR-3 to 5 exoribonuclease- Starts at 3 UTR 5 3 5 3 5 RNA Capping 5 RNA Capping: The chemical modification of the 5 UTR end of the mRNA to protect it from degradation by 5 to 3 exoribonucleases 5 Capping Occurs during transcription Protects 5 UTR end of RNA from degradation by 5 to 3 exoribonucleases Nascent mRNA can be capped even as transcription is still occurring 5 RNA capping consists of 2 steps:...
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This note was uploaded on 08/11/2010 for the course IPHY 3060 taught by Professor Allen,davi during the Fall '09 term at Colorado.

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Lecture 5 RNA Processing (Capping and Polyadenylation and the Regulation of mRNA Stability)

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