Transcription ; Holoenzyme complex; Inhibitors of Baterial RNA polymerase

1. Transcription
Presented ,
Mr-Pradeep D Devkate
M.Sc Microbiology, B.Ed, MH-SET, 2-GATE(Biochemistry, Zoology,
Botany) , Ph.D. pursing .

3. Transcription
• Transcription converts a gene into a single-stranded RNA molecule.
• Transcripts
• P=Promoter
• T=Terminator
• Transcripts
• m-RNA , mi-RNA, si-RNA, scRNA, r-RNA, sn-RNA, g-RNA, t-RNA, sno-RNA.
• Only m-RNA- coding RNA..
• Direction of Transcription 5’3’.
• Template strand direction 3’5’.

4. The central dogma states that information flows in one
direction from DNA to
RNA to
proteins.

5. Transcription key points
• Direction of Transcription 5’3’.
• Template strand (DNA) direction 3’5’.
• Rate of transcription 40 nucleotide / sec
• No requirement of primers
• Only one strand is used as Template during the transcription
• Synthesized RNA from only 6-8 nucleotide duplex with DNA
• Multiple round of transcription can be initiated by promoter .

6. • In transcription only addition of rNTPs (ATP,UTP,CTP,GTP)
• In transcription only selective portion of genome is transcribed
• In transcription one gene was multiple times copied
• Transcription error Rate
1 in 10000
Proofreading activity is present
Pyrophosphate editing
Hydrolytic editing –Gre-B Protein

7. Gene- segment of DNA which can transcribe.
Rewind
unwind

9. Template strand
Antisense strand
Non-Template strand
Sense strand

10. Prokaryotic – single core enzyme-RNA Polymerase
• enzyme-RNA Polymerase made – 5-subunits- α2, β, β’, ω .
• Single core enzyme associated with different σ factors = Active
different Holoenzyme complex

11. α- subunit
weak affinity for promoter. DNA binding
ability.
 Arg-R-chain ADP Ribosylation now RNA
polymerase do not bind to DNA
β-Subunit
Major and catalytic subunit
(5’3’ Polymerase activity)

12. • β’-Subunit
 Hold Template DNA in single stranded state.
 site for co-factor binding(Mg++)
• ω-subunit
No known function
Probably has role in polymerase assembly formation

13. Holoenzyme = RNAP + σ factors
• In a Bacteria single RNA Polymerase which are interact with different
σ- factors - activation of different gene ..
Initiation factor σ factors ..
Nif gene

14. Holoenzyme = RNAP + σ factors
• In bacteria single core RNA Polymerase
• In Bacteria having different ( Holoenzyme) RNA polymerase
• Core RNA polymerase are able to initiation of transcription
• But in presence of sigma factor Transcription efficiency increase by
10000 fold

15. RNA Exit channel
DNA entry channel

16. Inhibitor of Bacterial RNA Polymerase
Antibiotics – Rifampicin - β- -subunit-- initiation
Streptoglydigin –β--subunit- Elongation

18. Is binding site of RNA polymerase Is dissociation site of RNA Polymerase

19. Same Template Utilized DNA Polymerase(1000nt/Sec) and RNA Polymerase(40 nt/sec)
RNA Polymerase dissociate
DNA Synthesis forward

21. Terminator Sequence
Start site
5’
3’
3’
5’
-10bpSequence(6bp)=TATAAT
-35bpSequence(6bp)=TTGACG
Spacer Sequence- Are not conserved
Spacer sq
Conserved sequence More similar
Upstream Downstream
Upstream – In upstream sequence - Promoter , Operator (Regulatory sequence)
Downstream-- In Downstream sequence - Coding sequence, Terminator Sequence

23. ?????????????
Thank You……

25. DNA Dep DNA Polymerase =
RNA Dep DNA Polymerase =
DNA dep RNA polymerase =