MCB 252 Topic 13 mRNA Processing mRNA Turnover and Regulation of Translation part 1 Prof David Rivier MCB 252 Spring 2015 Reading Lodish sections 8 1 and 8 3 Lecture Outline Overview of RNA processing mRNAs Specificity of Splicing A bit about poly adenylation Processing is Co transcriptional mRNA export mechanism and logic Non sense mediated decay 5 Capping Where does the specificity for splicing come from Where does the specificity for splicing come from From MCB 250 Splicing and Information Content ESE Exonic Splicing Enhancer SR proteins contribute specificity to direct splicing SR proteins bind 6 nt sequences 46 4096 possible sequences 238 enriched in exons ESEs 238 4096 5 8 RRM RNA Recognition Motif Start site CP Gene 40 50 Transcription Pre mRNA Capping Cleavage Pre mRNA processing Polyadenylation Pre mRNA Poly A Splicing mRNA Export Poly A Pre mRNA processing is co transcriptional TAFs IIB TBP Capping CBC enzymes RN P RNP RNP P RN RNP RNP RNP RNP RNP RNP RNP CBC CBC Cap Binding Complex CBC 20 80 RNP RiboNucleoProteins RNP Nascent RNP particle CBC Pre mRNA processing is co transcriptional EJC Exon Junction Complex Lariat Spliceosome EJC P RNP RN RNP RNP RNP RNP CBC P N RNP R RNP RNP RNP RNP CBC Pre mRNA processing is co transcriptional A role for the CTD processing elongation and termination RRN NPP EJC RRNN PP RNP RNP P RN RNP RRNN PP RNP RRNN PP NP C R J E RNP RRN NPP RRNN PP RNP RRNN PP RNP RNP EJC RNP P RNP EJC RN RNP P RNP RN RNP RNP RNP RNP CBC Cleavage and II AA A A PAABAPA A A A Polyadenylation AII PAAA P A B A BPAI P A factors AI A A EJC EJC C CB Poly A tail is 250 residues 1 PABPII for 12 residues New Question RRN NPP EJC RRNN PP RNP Ribonucleoprotein or RNP particle RRNN PP P RN RRNN PP RNP RNP RRN NPP RRNN PP EJC RNP RRNN PP NP C R J P E RN AA AAABAPA AAAP I A I P A II AA B A P A A APA ABA PAII P RN C CB How are RNP particles exported to the cytoplasm mRNA export mRNA export MPMV Mason Pfizer Monkey Virus RNA virus Unlike HIV MPMV does not code for Rev or a Rev equivalent Accordingly there is no RRE in the MPMV sequence In contrast the MPMV viral RNA contains a Constitutive Transport Element CTE that is responsible for its nuclear export CTE secondary structure Surprisingly MPMV does not code for a CTE binding protein mRNA export CTE Cellular factor MPMV RNA MPMV virions mRNA export Tap P15 heterodimer is the major mRNA exporter CTE Cellular Tap factor P15 5 3 MPMV RNA Tap P15 5 3 Cellular mRNAs do not have CTEs mRNA export RNP PP RRNN RNP RN P EJC PP RRNN R RNP NP RNP CBC Tap P15 RNP II AA APAAA BPAIA APA IA A PAAB RN P RNP RN P PP RRNN EJC EJC AA NPP RRN Export AA AIIA BP PA RN P AA RNP Ta p P1 RRN 5 NPP EJC Ta p P1 5 P RN EJ C A P A A P RN P RN RNP Ta NPP RRN NPP p RRN RRN N P P P1 RRN NPP RRNN 5 PP RRN NTaPP EJC II A A A AA A P A B A A P PAA AA BPAIAI A I I A A BAP P RN CCBB CC PRR1NN 5PP p RNP CB CBCC Ta p P1 5 P RN EJC RNP P RN RNP PRR1NN 5PP p RRNN PP RRN NTaPP Ta p RRPN N 1P5P P N R EJC N NPP RR EJ C T ap RRN NPP P15 P RN NPP RRN P RN RRN NPP A P A A II A A A ABAPAA A A P PAA A A BPAIAI A I I A A BAP EJC Ta p P1 5 P RN RNP P RN P RN CBC RNP PRR1NN 5PP p RRNN PP RRN NTaPP NPP RRN EJC P RN NPP RRN Ta p P1 5 RRNN PP C EJ P RN Ta p P1 5 RRN NPP RRN NPP A P A A II A A A ABAPAA A A P PAA A A BPAIAI A I I A A BAP T P1 a p 5 RNP RNP RRN NPP RNP RN P Tap P15 RRNN PP C EJ RRN NPP RNP P RN P RN EJC Ta p P1 5 Ta p P1 5 P RN P RN P RN EJC NPP RRN RRN NPP A P A A II A A A ABAPAA A A P PAA A A BPAIAI A I I A A BAP CBC A PAABAPA A A II AA A A A I I A BAP PAAA A A P A BPA IAI P RN P RN RN P RNP T P1 ap 5 RNP A P RN RNP P RN Ta P1 p 5 C EJ RNP P RN C EJ Ta p P1 5 RRNN PP RNP CBC RNP P RN Tap P15 EJC eiF4E P RN P RN P RN RNP Ta P1 p 5 Ta p P1 5 P RN CBC RNP RNP P RN P RN RNP PPAABBAPPA AA A III AA A A I A I P I A A BBP A PAAA A P A P A BBPPAI I AI A RNP RN P RNP Tap P15 C EJ EJC EJC eiF4E A A APABAPAI AA A A I A AA ABP A A P PAA AA BAP A I mRNP particle C EJ C EJ EJC eiF4E mRNA export Lecture Outline Overview of RNA processing mRNAs Specificity of Splicing A bit about poly adenylation mRNA export mechanism and logic Non sense mediated decay mRNA export EJC EJC PA IAAAPAAABA I AA P B A A A PA AA P ABAP AA A AI EJC One round of translation EJC EJC eiF4E A A C EJ PAAABPI I AAAAAP A P A BAA AA P A AAAB AA APAI eiF4E Protein mRNA controlled degradation 60S Full length Protein EJC EJC 5 UTR EJC 40S 3 UTR AAA 200 mRNA controlled degradation EJC s play a role in quality control 60S Truncated Protein EJC EJC 5 UTR EJC 40S 3 UTR AAA 200 mRNA controlled degradation 5 UTR EJC Non sense mediated decay deadenylase 3 UTR AAA 200 Exosome