RNA Biosynthesis（transcription）RNA的生物合成.ppt

1、RNA Biosynthesis (Transcription),1复制和转录过程有什么相似之处？又各有什么特点？2. 试述真核细胞RNA转录后的加工修饰,Concept The process of copying DNA to RNA by an enzyme called RNA polymerase (RNAP) The transfer of genetic information from DNA into RNA,transcription,Content,Templates and Enzymes The Process of Transcription Post-transc

2、riptional Modification,The difference between replication and transcription,Substances for transcription,Substrates: NTP (ATP, UTP, GTP, CTP) Template: DNA Enzyme: RNA polymerase( RNA-pol) Other protein factors,Templates and Enzymes,Section I,Template for transcription,Structural gene : a DNA fragme

3、nt coding for any RNA or protein product other than a regulatory element Template strand (sense strand or Watson strand) : the strand of DNA that the RNA polymerase uses as a template to produce complementary mRNA Coding strand (antisense strand or Crick strand) : the strand that is not used as the

4、template it has the same base sequence as the RNA transcript produced (although with thymine replaced by uracil),5GCAGTACATGTC 3,3 c g t g a t g t a c a g 5,5GCAGUACAUGUC 3,NAla Val His Val C,Coding stand,Template strand,mRNA,Protein,transcription,translation,5 3,3 5,Template strand,Coding strand,Co

5、ding strand,Template strand,Structural gene,Asymmetric transcription,certain region of only one strand of DNA serves as a template for transcription The template stand is not always restricted to the same single DNA strand,RNA polymerase,Prokaryotic RNA polymerase,core enzyme,holoenzyme,The binding

6、site of RNApol holoenzyme on the transcription initiation region,Eukaryotic RNA polymerase,A site for RNA pol to identify and bind on the template,Operon: a unit of transcription in prokaryotes including one or more structural genes and upstream regulon,promoter : the site on the template DNA for RN

7、A pol binding,RNA polymerase protectionassay,目 录,Transcription initiation,T T G A C A A A C T G T,-35 region,(Pribnow box),T A T A A T Pu A T A T T A Py,-10 region,Prokaryotic promote conservative sequence,recognition site,Structural gene,-GCGC-CAAT-TATA,Eukaryotic promote conservative sequence,The

8、Process of Transcription,Section II,Initiation,Two issues required to be addressed the binding of RNA polymerase to the initial region of the transcription template precisely only one strand of DNA, the template strand, is used to produce mRNA,Prokaryotic transcription,The DNA is unwound and becomes

9、 single-stranded in the vicinity of the initiation site (defined as +1).,RNA pol holoenzyme (2) specifically binding to the promoter region on DNA,1st poly reaction catalyzed by RNA pol and transcription initiation complex is formed,RNApol (2) - DNA - pppGpN- OH 3,transcription initiation complex,5-

10、pppG -OH + NTP 5-pppGpN - OH 3 + ppi,Initiation,Elongation, subunit dissociates from the holoenzyme ，and elongation proceeds,with the effect of the core enzyme，NTP maintain polymerization，RNA strand elongated,(NMP) n + NTP (NMP) n+1 + PPi,transcription bubble：,RNA-pol （Core enzyme ） DA RNA,目 录,目 录,5

11、,3,DNA,Feather phenomena during prokaryotic transcription,ribosome,RNA,RNA pol,Rho () factor dependent transcription termination Rho-independent transcription termination,Termination,The process of the RNA polymerase stopping on DNA template and the dissociation of the RNA from the transcription com

12、plex,Classification,A T P,Rho () factor dependent transcription termination,Termination independent on Rho factor,The terminator sequence within the RNA for the stop of RNA polymerase. The terminator sequence usually forms a stem-loop hairpin structure leading to the dissociation of the RNAP from th

13、e DNA template,5UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU. 3,5UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU. 3,RNA,5TTGCAGCCTGACAAATCAGGCTGATGGCTGGTGACTTTTTAGTCACCAGCCTTTTT. 3,DNA,5UUGCAGCCUGACAAAUCAGGCUGAUGGCUGGUGACUUUUUAGUCACCAGCCUUUUU. 3,stem-loop/hairpin structure,Mecha

14、nism involved in the termination by stem loop,allosteric change of RNA poly for the stop of transcription dissociation of transcription complex for the release of RNA,Eukaryotic transcription initiation,initiation,A variety of upstream control elements exist RNA-pol does not directly bind to the tem

15、plate in the initiation Much more complicated than prokaryotic transcription,Transcription Initiation n site,TATA box,CAAT box,GC box,enhancer,cis-acting element,The upstream region from the transcription initiation,AATAAA,Excision and adding tail,Transcription Termination site,Modification site,exo

16、n,Translation initiation site,intron,OCT-1,OCT-1：ATTTGCAT octamer,Transcription factor,Trans-acting factors : The proteins with ability to recognize and bind directly or indirectly to the upstream control element of DNA Hundreds factors have been reported,Transcriptional factors (TF): Among the tran

17、s-acting factors, the proteins with ability to bind directly or indirectly to RNA pol,参与RNA-pol转录的TF,Pre-initiation complex ( PIC),Eukaryotic transcription initiation require a variety of transcription factor because of the indirectly binding of Eukaryotic RNA-pol to DNA,TFF,A,B,PIC transcription ca

18、talyzed by RNA-Pol ,H,E,TBP,TAF,TFD-A-B-DNA complex,TATA,A,B,TBP,TAF,TATA,H,E,After PIC assemble，CTD phosphorylation by TFH,Piecing theory,The eukaryotic transcription requires 3 to 5 TF binding together and becoming the complex for the activation of specific gene transcription,Elongation,Similar to prokaryotic transcription elongation. synchronous transcription and translation is not observed because of segregation of nuclear membrane,The forward moving process of