110 likes | 301 Views
Chapter 14 RNA Processing I : Splicing. Summary of splicing Transcription Primary transcript splicing mature transcript. Evidences for introns R-loop in the electron microsopic view of chromatin sequencing ; compare genomic DNA and cDNA. Splicing signals and mechanism.
E N D
Chapter 14 RNA Processing I : Splicing
Summary of splicing • Transcription • Primary transcript • splicing • mature transcript • Evidencesfor introns • R-loop in the electron microsopic view of chromatin • sequencing ; compare genomic DNA and cDNA
Splicing signals and mechanism Lariat structure Introns almost all start with GU and end with AG Branch point Spliceosome ; pre-mRNA, snRNPs (snurps); protein RNA ; U1,2,4,5,6
Spliceosomal pre-mRNA U6 U2 U5
The spliceosome cycle Model for participation of CTD in exon definition - The CTD acts as a platform for the gathering of pre mRNA and splicing factors.
Alternative splicing Ex) Mu RNA; secreted form and membrane-bound form Sex determination in Drosophila ; 8 chromosomes (X/Y, 2, 3, 4 autosomes) male = XY female= XX Sxl activates tra activates dsx to determine female.
serendipity Self-splicing RNAs Group I intron Group II intron Thomas Cech ; Nobel prize 1989 Any possibility of contamination of spliceosome in the in vitro transcription? chemically synthesize the precursor splicing still occurs Tetrahymena (ciliate)
Group I intron GTP
Spliceosomal pre-mRNA Group II intron U6 Group II intron’s splicing - - - mechanism is similar to pre mRNA’s splicing - They have A at the branch point. U2 U5
Is self-splicing RNA true enzyme? Phe • CatalyticRNA = Ribozyme • self-splicing RNA • M1 RNA of RNase PI • Telomerase • CoTc 5’ RNaseP