Chapter elevenRNA transcription.pptVIP

Explanation 2. It is also carried out in nuclear. 3. It is also earlier than the splicing . 4. It can protect mRNA 3’-terminal from nuclease. 5. The mRNA 3’-terminal of prokaryote doesn’t have the polyA tail structure. 1. The polyA tail is independent on DNA template. 6. It relates with protein translation . P H N N N N H2N O OCH3 CH2 O O- O O P O- O O P O- O O O OH OH H2C P O- O O ……AAAAAAAA-OH 7 CH3 O N 5’ 5’ O mRNA splicing enzyme DNA double strand 5’ intron-1 intron-2 intron-3 exon-1 exon-3 exon-4 exon-2 5’ hnRNA strand split gene splicing of hnRNA 5’ hnRNA strand mRNA lariat structure transcription and past-transcribed modification for albumin gene A B C D E F G L 1 2 3 4 5 6 7 5’ 47 185 51 129 118 143 156 1043 gene-7.7kb 5’ hnRNA transcription AAA AAA m7G5’ppp5’ m2’G 5’ modification modified mRNA AAA AAA 5’ lariat mRNA to form lariat m7G5’ppp5’ m2’G AAA AAA 5’ mature mRNA splicing m7G5’ppp5’ m2’G AG……. UCCAUACAUAPPPGm AUGAUGU PPPGm exon-1 exon-2 intron-1 U1-snRNA U2-snRNA pG-O-H ….....AGGUAUGU UACUACA kinds of introns and its way of splicing 1. It is in the rRNA gene mainly. 2. It is in the protein-coding gene of mitochondrion and chloroplast. self-splicing RNA=ribozyme 3. It is in the most protein coding gene. lariat way, by small nuclear ribonucleoprotein requires enzyme and ATP 4. It’s in the tRNA gene. What is the functions of introns in gene? Process after transcription for tRNA 1. Splicing . 2. To form rare base. 3. Addition of 3’-terminal CCA-OH. 3’ OH U U primary transcript 5’ splicing of primary transcript for tyrosine-tRNA in yeast 3’ OH U U 5’ spliced tRNA 5’ tRNA gene to form rare base in transcript of tyrosine-tRNA in yeast 1. methylation: catalyzed by tRNA-methyltransferase, A Am, G Gm, C C m spliced tRNA 3’ OH U U 5’ G G G A C 3’ OH U U 5’ Gm Gm Gm Cm