Transcription process explained ppt 1234

Transcription

1. Welcomes you for the FREE DEMO CLASS BioNETVision

2. 3B; RNA synthesis and processing Dr. Rajsekhar Bhowmick BioNETVision

3. Transcription factors and machinery, formation of initiation complex, transcription activators and repressors, RNA polymerases, capping, elongation and termination, RNA processing, RNA editing, splicing, polyadenylation , structure and function of different types of RNA, RNA transport.

4. RNA Polymerase Holoenzyme could transcribe intact phage T4 DNA in vitro quite actively, the core enzyme had little ability to do this. On the other hand, core polymerase retained its basic RNA polymerizing function because it could still transcribe highly nicked templates very well

5. σ as a Specificity Factor

6. σ as a Specificity Factor The σ factor confers specificity for the T4 immediate early genes

7. σ as a Specificity Factor Testing for asymmetric or symmetric transcription in vitro

8. If there is no correct initiation of transcription. Which subunit of RNA polymerase holoenzyme would have defect in (Dec 2006) α- subunit β-Subunit β’- Subunit σ- Subunit

9. σ-subunit of E.coli RNA polymerase does not (June-2013): Initiate transcription and fall off during elongation. Increase affinity of the core enzyme to the promoter Binds to DNA, independent of the core enzyme. Ensure specificity of transcription by interacting with the core enzyme.

10. Bacteriophage T4 infects E. coli injects its DNA inside the cell. The transcription of viral genes occurs in three stages: immediate early, early and late. All the promoters on viral genome are available, but the control takes place at the level of: (June-2013): Promoter strength. Modification of host RNA polymerase. Synthesis of new polymerases. Turn over rate of RNA synthesis.

11. Prokaryotic Vs Eukaryotic RNA Pol Pol I transcribes the large rRNA precursor gene, whereas Pol III transcribes tRNAgenes , some small nuclear RNA genes , and the 5SrRNA gene. Two more DNA-dependent RNA polymerases have been identified in recent years, and have been called Pol IV and Pol V. These are found only in plants,where they transcribe small interfering RNAs involved in transcriptional silencing

12. Which eukaryotic RNA polymerase transcribes t-RNA genes? (Dec-2010) RNA polymerase I RNA polymerase II RNA polymerase III DNA polymerase I

13. Initiation

14. Promoters

15. How does σ change the way the core polymerase behaves toward promoters? The σ-factor allows initiation of transcription by causing the RNA polymerase holoenzyme to bind tightly to a promoter.

16. Stages of transcription initiation

17. Sigma seems to stimulate both initiation and elongation .

18. The σ cycle

19. FRET Assay to σ movement relative to DNA

20. Local DNA Melting at the Promoter

21. During Initial Transcription, RNA Polymerase Remains Stationary and Pulls Downstream DNA into Itself

22. Extent of Polymerase Binding to Promoters

23. Elongation

24. Termination of Transcription

25. Function of Rho

26. The Elongating Polymerase Is a Processive Machine That Synthesizes and Proofreads RNA pyrophosphorolytic editing. hydrolytic editing RNA Polymerase Can Become Arrested and Need Removing: TRCF and UVR A,B and C

27. Sensitivity of purified RNA polymerases to α- amanitin

28. Α- amanitin inhibits (Dec-2011) Only RNA Pol I. Only RNA Pol II. Only RNA Pol III All RNA Pol.

29. Eukaryotic promoter Class I Class II Class III

30. Promoters for RNA Pol III located at(Dec 2009) +1 to +10 -35 to -10 Within transcribed sequence Downstream after initiation

31. TFIID contains a 38-kD TATA boxbinding protein (TBP) plus several other polypeptides known as TBP-associated factors TFIID, apparently with help from TFIIA, binds to the TATA box, TFIIB binds next, causing minimal perturbation of the protein–DNA interaction. TFIIF helps RNA polymerase bind to a region extending from at least position –34 to position +17. The remaining factors bind in this order: TFIIE and TFIIH, forming the preinitiation complex . TFIIH has a DNA helicase activity that is essential for transcription

32. In order to study the transcription factor TFIIH, it was cloned from a large number of human subjects. Surprisingly, the subjects having mutation in TFIIH, also showed defects in their DNA repair system. Given below are the explanations: DNA damage is always associated with transcription inhibition. TFIIH has no role in DNA repair. In mammalian system, TFIIH plays an active role in transcription coupled DNA repair process. Because of mutation in TFIIH, transcription initiation is inhibited and remain attached to the template DNA leading to DNA damage. Choose the correct answer. (June-2015) A and B. B and D. C only D only

33. TATA less Promoter

34. Class III Promoter

35. Capping

36. Capping

37. Capping

38. Function of Capping Protection of the mRNA from degradation; Enhancement of the mRNA’s translatability; Transport of the mRNA out of the nucleus; and Proper splicing of the pre-mRNA.

39. Polyadenylation An efficient mammalian polyadenylation signal consists of an AAUAAA motif about 20 nt upstream of a polyadenylation site in a premRNA , followed 23 or 24 bp later by a GU-rich motif, followed immediately by a U-rich motif. Many variations on this theme occur in nature, which results in variations in efficiency of polyadenylation . Plant polyadenylation signals also usually contain an AAUAAA motif, but more variation is allowed in this region than in an animal AAUAAA. Yeast polyadenylation signals are more different yet, and rarely contain an AAUAAA motif.

40. The 3’ end of most eukaryotic mRNAs is defined by addition of a plyA tail- a processing reaction called polyadenylation . The addition of polyA tail is carried out by the Enzyme Poly(A) polymerase. Given below are few statements about this process: Poly(A) Polymerase is a template independent enzyme. Poly(A) Polymerase catalyses the addition of AMP from dATP to the 3’ end of the mRNA. Poly(A) Polymerase is a RNA-template dependent enzyme. Poly(A) Polymerase catalyses the addition of ADP from ATP to the 3’ end of mRNA. Poly(A) Polymerase catalyses the addition of AMP from ATP to the 3’ end of mRNA. Poly(A) Polymerase catalyses the addition of AMP from dADP to the 3’ end of mRNA. Which of the following combination is true? (June-2015) B and C. C and D. A and E. C and F

41. Splicing

42. In type II splicing. (June-2015) A G’-OH from outside makes a nucleophilic attack on 5’P of first base intron . A free 2’O of an internal adenosine makes a nucleophilic attack on 5’P of first base of intron . A 3’O of an internal adenosine makes a nucleophilic attack on 5’P of first base of intron . The hydrolysis of lastbase of exon is carried out by U2/U4/U6

43. Alternative Splicing

44. Trans Splicing

45. Leader sequence in some of the protozoan parasite is transcribed elsewhere in the parasites genome and gets joined with several transcripts to make the functional RNA. The joining of the two transcripts occur by the process of (Dec-2014) Alternative splicing. Trans splicing. Ligation. RNA editing.

46. RNA editing

47. With an intention to identify the genes expressed in an organism at specific stage of development, mRNAs were isolated from the given organism, cDNAs were synthsized , cloned in a suitable vector and sequenced. A few of the cDNA sequences showed no matches with the genomic DNA sequence. Further, it was observed that these sequences were U rich and found to be in stretches dispersed along the sequence. The following may be possible reason for appearance of such RNA: Splicing. Alternate Splicing. Trans Splicing. Guide RNA mediated introduction of Usinvoving endonuclease , terminal-U- Transferease and RNA ligase . Determination converting C to U. Which of the followinh is the most appropriate reason/s? (June-2015) A and C. B and D. C, D and E. D only

48. Thank You