分子生物学2--rnaprocessing(编辑修改稿)

分子生物学2--rnaprocessing(编辑修改稿)内容摘要：

TS。 THE MECHANISM IS SIMILAR TO NORMAL CISSPLICING WEAVER: FIG. Spliced leader 35nt Werner Syndrome (WS), an autosomal recessive human geic disease that mimics premature aging. Normal ttttaatag GGTAGAAAT Werner c A WS mutation leads to abnormal splicing Science 1996, 272:258 3’ splice site G l y A r g A s n mRNA Capping • occurs at the 539。 end of mRNA via addition of a 539。 539。 PPP linkage of a guanosine. • occurs cotranscriptionally • may be required for stability of the mRNA export from the nucleus mRNA splicing translation. Capping of the 5’ end of nascent RNA transcripts with 7methylguanylate (m7G). m mRNA Polyadenylation* * Note: Most eukaryotic mRNAs contain 20250 A at 339。 ends, a major exception are histone mRNAs. A few procaryotic mRNAs contain poly(A) tails. 5’ …. AATAAA..(1120bp)…CA….TTGTGTGTTG..3’ 3’ …. TTATTT………...…GT….AACACACAAC..5’ 5’ …. AAUAAA…( 1120b)…CA….UUGUGUGUUG..3’ Polyadenylation signal Cleavage site polyA adddition site GU rich 典型 的聚腺苷化位点 DNA RNA A MODEL OF THE PRECLEAVAGE COMPLEX CPSF: CLEAVAGE AND POLYADENYLATION SPECIFICITY FACTOR CstF: CLEAVAGE STIMULATION FACTOR CF I/II: CLEAVAGE FACTORS PAP: POLY(A) POLYMERASE WEAVER: FIG. Function of Polyadenylation • Transcription termination • Stability of mRNAs in eukaryotes • translation efficiency • Element associated with 339。 terminal intron removal EFFECT OF POLYADENYLATION ON TRANSLATABILITY AND STABILITY (a) TRANSLATABILITY in vitro (b,c) STABILITY in vitro WEAVER: FIG. Poly(A)+ Poly(A) cap+ cap RNA Pol II functions in various RNA processing Genes amp。 Dev (20xx), 14:1415 RNA Editing A process in which information changes at RNA level Two General Types of RNA Editing • Insertion/Deletion • Substitution/Modification RNA editing of apoB premRNA. The apoB mRNA produced in the liver has the same sequence as the exons in the primary transcript. This mRNA is translated into ApoB100, which has two functional domains: a Nterminal domain (green) that associates with lipids and a Cterminal domain (orange) that binds to LDL receptors on cell membranes. In the apoB mRNA produced in the intest。