清华大学：《分子生物学》课程PPT教学课件（基因ene）第二十二章 核的剪切（Nuclear splicing）

Chapter 22 Nuclear splicing 清革大当

Chapter 22 Nuclear splicing

22.1 Introduction 22.2 Nuclear splice junctions are short sequences 22.3 Splice junctions are read in pairs 22.4 Nuclear splicing proceeds through a lariat 22.5 snRNAs are required for splicing 22.6 Ul snRNP initiates splicing 22.7 The E complex can be formed in alternative ways 22.8 5 snRNPs form the spliceosome 22.9 An alternative splicing apparatus uses different snRNPs 22.10 Group II introns autosplice via lariat formation 22.11 Alternative splicing involves differential use of splice junctions 22.12 cis-splicing and trans-splicing reactions 22.13 Yeast tRNA splicing involves cutting and rejoining 22.14 The unfolded protein response is related to tRNA splicing 22.15 The 3 ends of poll and polllI transcripts are generated by termination 22.16 The 3c ends of mRNAs are generated by cleavage 22.17 Cleavage of the 3c end may require a small RNA 22.18 Production of rRNA requires cleavage and modification events 22.19 Small RNAs are required for rRNA processing 清菜大当

22.1 Introduction 22.2 Nuclear splice junctions are short sequences 22.3 Splice junctions are read in pairs 22.4 Nuclear splicing proceeds through a lariat 22.5 snRNAs are required for splicing 22.6 U1 snRNP initiates splicing 22.7 The E complex can be formed in alternative ways 22.8 5 snRNPs form the spliceosome 22.9 An alternative splicing apparatus uses different snRNPs 22.10 Group II introns autosplice via lariat formation 22.11 Alternative splicing involves differential use of splice junctions 22.12 cis-splicing and trans-splicing reactions 22.13 Yeast tRNA splicing involves cutting and rejoining 22.14 The unfolded protein response is related to tRNA splicing 22.15 The 3¢ ends of polI and polIII transcripts are generated by termination 22.16 The 3¢ ends of mRNAs are generated by cleavage 22.17 Cleavage of the 3¢ end may require a small RNA 22.18 Production of rRNA requires cleavage and modification events 22.19 Small RNAs are required for rRNA processing

21.1 Introduction RNA splicing is the process of excising the sequences in RNA that correspond to introns,so that the sequences corresponding to exons are connected into a continuous mRNA. pre-mRNA heterogeneous nuclear RNA (hnRNA). hnRNP 清苇大当

RNA splicing is the process of excising the sequences in RNA that correspond to introns, so that the sequences corresponding to exons are connected into a continuous mRNA. pre-mRNA heterogeneous nuclear RNA (hnRNA). hnRNP 21.1 Introduction

22.1 Introduction Figure 22.1 hnRNP hnRNA 200A 40S exists as a ribonucleopr otein particle 500-800 bases RNA_ organized as Core proteins (~30-40 kD) a series of beads. A1 A2 B1 B2 C1 C2 清菜大当

Figure 22.1 hnRNA exists as a ribonucleopr otein particle organized as a series of beads. 22.1 Introduction

22.1 Introduction 4o2 Figure 22.2 RNA is modified in the nucleus by Cap at 5 en PolyA at 3 end additions to the5￠and3￠ ends and by splicing to remove the introns.The NUCLEUS 200 splicing event requires breakage of the exon-intron junctions and joining of the ends of the exons;the Transation CYTOPLASM expanded illustration shows 200 the principle schematically, but not the actual order of exon intron exon events.Mature mRNA is Exon-intron junctions are b ken transported through nuclear pores to the cytoplasm, Exons are joined where it is translated. 清菜大兰

Figure 22.2 RNA is modified in the nucleus by additions to the 5￠ and 3￠ ends and by splicing to remove the introns. The splicing event requires breakage of the exon-intron junctions and joining of the ends of the exons; the expanded illustration shows the principle schematically, but not the actual order of events. Mature mRNA is transported through nuclear pores to the cytoplasm, where it is translated. 22.1 Introduction

22.2 Nuclear splice junctions are interchangeable but are read in pairs GT-AG rule describes the presence of these constant dinucleotides at the first two and last two positions of introns of nuclear genes. Splice sites are the sequences immediately surrounding the exon-intron boundaries. 情菜大兰

GT-AG rule describes the presence of these constant dinucleotides at the first two and last two positions of introns of nuclear genes. Splice sites are the sequences immediately surrounding the exon-intron boundaries. 22.2 Nuclear splice junctions are interchangeable but are read in pairs

22.2 Nuclear splice junctions are interchangeable but are read in pairs Left (5)site Right(3)site Ex64G73G10062463 12Py N C6A1010N Exon Intron Figure 22.3 The ends of nuclear introns are defined by the GT-AG rule 清苇大当

Figure 22.3 The ends of nuclear introns are defined by the GT-AG rule 22.2 Nuclear splice junctions are interchangeable but are read in pairs

22.2 Nuclear splice junctions are interchangeable but are read in pairs Comrect splicing removes 3 introns by pairwise recognition ofthe junctions GU GU GU Figure 22.4 Splicing junctions are P airing of wrong junctions would remove exons as well as introns,but aberant products are not found recognized GU GU only in the correct pairwise GU GU rGU combinations. 清菜大当

Figure 22.4 Splicing junctions are recognized only in the correct pairwise combinations. 22.2 Nuclear splice junctions are interchangeable but are read in pairs

22.2 Nuclear splice junctions are interchangeable but are Thevector contains two exons that are spliced together in the transcript promoter5'splice junction 3splice junction Figure 2.20 A special exon int ron exon splicing vector is used for exon trapping.If an A genomic fragment is inserted into the intron;any exon in the exon is present in the fragment will be found in the RNA Genomic fragment genomic fragment,its intron exon intron sequence will be Insert into recovered in the cloning site cytoplasmic RNA,but if the genomic fragment consists exon intron exon intron exon solely of an intron, Transcription splicing 清第大当

Figure 2.20 A special splicing vector is used for exon trapping. If an exon is present in the genomic fragment, its sequence will be recovered in the cytoplasmic RNA, but if the genomic fragment consists solely of an intron, 22.2 Nuclear splice junctions are interchangeable but are read in pairs

Gene 5.6 kb 22.2 Nuclear splice junctions 11121314■516171 are interchangeable but are read in pairs mRNA=1.1 kb Figure 22.5 Northern Primary transcript(5.5 kb) blotting of nuclear RNA with an ovomucoid probe identifies discrete Lacks introns 5 6 precursors to mRNA.The Lacks introns 4,5,6,&7 contents of the more prominent bands are Contains only intron 3 indicated.Photograph kindly provided by Bert O'Malley. mRNA (1.1 kb) 清菜大当

Figure 22.5 Northern blotting of nuclear RNA with an ovomucoid probe identifies discrete precursors to mRNA. The contents of the more prominent bands are indicated. Photograph kindly provided by Bert O'Malley. 22.2 Nuclear splice junctions are interchangeable but are read in pairs