分子生物學(xué)2--rnaprocessing-資料下載頁
2025-05-19 18:54本頁面
【導(dǎo)讀】Processing. Transport. Localization. RNAstability. Translation. Splicing. Capping. Polyadenylation. Editing. rRNAMaturation. tRNAMaturation. Self-splicing. Tran-Splicing. Historyofdiscovery. WEAVER:FIG.VERTEBRATES:5’-AG/GUAAGU---intron---YNCURAC--(Y)n--NAG/G-3’。YEAST:5’-NN/GUAUGU---intron---UACUAAC---------YAG/G-3’。WEAVER:FIG.U4:achaperoneforU6. U1snRNAbase-pairswith5'splicesiteofpre-mRNA;WEAVER:FIG.40-60Sparticles. RNAHelicases. SRproteins. U2AF
【正文】 ent of Bicoid protein. (C) Cell lineage specification. Localized RNAs are used in a variety of systems in which they are partitioned unequally into daughter cells or into blastomeres of embryos to determine a cell lineage. The case depicted is the localized RNAs involved in specifying the germ cell lineage in amphibians. (D) Association of RNA with different anelles or cell structures. This example is of the localization of cyclin B mRNA at the poles of the mitotic spindle. (E) Some RNAs are localized to a specific region of a cell or embryo to allow for localized translation such as RNAs at the synapses of neurons (red) . The Role of Secondary Structure in the Localization of Ash1 mRNA in Yeast. (Left) The normal distribution of ash1 mRNA to the daughter cell in yeast. (Right) The aberrant distribution of the RNA when mutations are made that effect the stemloop structure. mRNA localization signals reside in 339。 UTR mRNA Stability and Degradation mRNA halflives vary significantly for different mRNAs and anisms Cell Average Halflife Range of Halflife E. coli 3 5 min 2 10 min Yeast 22 min 4 40 miun Cultured mammalian cells 10 hrs 30 minutes or less (histone and cmyc) 24 hrs to days ( for GH) Elements or factors associated with mRNA stability/degradation 1. Cap 2. Poly A tail length (poly Abinding protein) 3. Destabilizing elements Within ORF Within UTRs (ARE) 4. Translation of mRNA (plex and not so clear) 5. Premature termination codons or nonsense codons mRNA Degradation Pathways ? Deadenylationdependent pathway mon general pathway for all mRNAs (Default) ? Deadenylationindependent pathway Prokaryotic vs eukaryotic gene expression PROKARYOTES EUKARYOTES One gene, several polypeptides Simple regulatory elements mainly within the promoter RNA pol can recognize the promoter No introns and exons Little posttranscriptional processing Transcription and translation are coupled One RNA pol One gene, one polypeptide Complex regulatory elements sometimes far away RNA pol needs other factors to interact with promoter Introns and exons Complex processing needed to generate mature mRNA Mature mRNA is exported from nucleus Three RNA pol
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