BCHM 4116 1st Edition Lecture 27Outline of Last Lecture I. Transcription initiation by RNA pol II requires TBP and GTFsOutline of Current Lecture 1. Eukaryotic Transcripts Processed and Delivered to Ribosome for TranslationCurrent Lecture29.5 – Eukaryotic Transcripts Processed and Delivered to Ribosome for Translationa. Transcription occurs on DNA in nucleus, and translation occurs on ribosomes in cytoplasmb. On way to cytoplasm, transcripts undergo processing to form mature RNA i. Eukaryotic genes are split genes 1. Exons – coding regions2. Introns – non-coding regions ii. Post-transcriptional processing of mRNA precursors involves capping, methylation, polyadenylylation, and splicing 1. Capping & methylation a. 5’-end of growing transcript is capped by addition of guanylyl residuei. catalyzed by guanylyl transferase using GTP b. Cap structure is methylated at the 7-position of the G residue i. Additional methylations may occur at 2’-O position o f2 nucleosides following 7-methyl-G cap at 6-amino group of 1st base adeninec. 3’-polyadenylylation i. Termination does not normally occur until RNA pol II transcribed past a consensus AAUAAA seq. knownas polyadenylylation signal1. Consensus AAUAAA is not poly(A)tail, instead it defines position where poly(A) addition occursii. A residues are not encoded in DNA but added post-transcriptionally by poly(A)polymeraseThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d. Splicingi. Splicing proceeds via formation of lariateii. Splicing depends on snRNPs1. snRNPs : U1, U2, U4, U5, U6 2. snRNPs form spliceosome a. splicesome = large complexi. Assembly requires ATPii. Assembly:iii. 1. U1 binds to snRNP @ 5’ splice site of pre-mRNAiv. U2 binds to snRNPv. Triple snRNP complex (U4/U6-U5) replaces U1 at 5’ splice site iii. Constitutive splicing : every intron is removed & every exon is incorporated iv. Alternative splicing1. Offers another level at which regulation of gene expression can
View Full Document
Unlocking...