Discussion section 0512

Discussion section 0512 - Discussionsection#6 TypesofRNA...

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Discussion section #6 05/12/08
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Types of RNA messenger RNA(mRNA)            later translated into a polypeptide transfer RNA(tRNA)            RNA molecules that carry amino acids to the growing        polypeptide ribosomal RNA(rRNA)            used in building of ribosomes small nuclear RNA(snRNA)            mediate some of the RNA processing steps micro RNA            These are tiny (~22 nts) RNA molecules that appear to regulate the      expression of mRNA molecules
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RNA processing 5’capping 3’poly A tail Splicing editing Export to cytoplasm
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5'-->5' linkage The 5' Cap (m 7 Gppp): Structure and function Several enzymatic reactions add the m7Gppp cap to pre-mRNA : 1. Step 1: γ -phosphate removal from 5 '-end of RNA 2. Step 2: Transfer of GM P from GTP to the 5 ' diphosphate. 1. Step 3: Transfer of methyl groups from S-adenosylmethionine to the N7 position and the 2 ' -oxygens of ribose (In animals and plants, not yeast) (In vertebrates) Functions of the cap: 1. Splicing 2. RNA stability 3. Export 4. Translation (recruiting ribosomes) Enzyme involved: RNA triphosphatase, capping enzyme(add GMP), guanine-7-methyl transfrase, 2’- O-methyltransferase
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AAAAA (100-250) Polyadenylation of mRNA 1 2 3 4 1 2 3 4 Factors co-transcriptionally bind two sequences in the RNA: the upstream AAUAAA signal the downstream GU- or U-rich sequence Poly(A) polymerase binds and facilitates cleavage at the poly(A) site. Bound poly(A) polymerase, in a slow phase, adds about 12 A’s to the 3' end of the RNA. Poly(A)-binding protein accelerates poly(A) addition by poly(A) polymerase. Functions of polyadenylation: 1. Protect 3'-ends of RNAs 2. Alternative processing generates different messages 3. RNA export 4. Translation (see p. 131 fig. 4-31)
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DNA/ mRNA  hybridization Loops Splicing occurs
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exons introns
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RNA splicing Consensus sequence Splicing reaction Spliceosome Alternative splicing
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Splice Site Consensus Sequences Yeast Mammalian 5' Splice site 3' Splice site Branch point Exon 1 Exon 2 GUAUGU UACUAAC PyAG Exon 1 Exon 2 GU A G AGN NNCUNAC PyAG Exon 1 Exon 2 Splicing
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This note was uploaded on 10/30/2010 for the course CHEM 114C taught by Professor Alexanderhoffmann during the Spring '08 term at UCSD.

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Discussion section 0512 - Discussionsection#6 TypesofRNA...

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