This document summarizes prokaryotic transcription. It describes that transcription involves RNA polymerase adding RNA nucleotides to a DNA template, similar to DNA replication but producing RNA. RNA polymerase requires a sigma factor to bind promoter regions containing -10 and -35 sequences. Transcription then proceeds through initiation, elongation, and termination stages. Initiation involves formation of open and closed complexes. Termination can be rho-independent using hairpin structures or rho-dependent using rho protein binding.

1. PROKARYOTIC
TRANSCRIPTION

2.  The process of synthesis of RNA
by coping the template strand of
DNA is called transcription
 Transcription is enzymatically
similar to DNA replication
 Both process involve enzyme that
synthesis new strands of nucleic
acid complementary to the DNA
strand.
 Major difference is that IN DNA
replication DNA polymerase add
deoxyribonucleic acid to the
template DNA.
 But in transcription RNA
polymerase add ribonucleic acid to
the template DNA.

3. RNA POLYMERASE ENZYME
•RNA polymerase enzyme has five subunits.
• Two alpha ( α ) subunit
• Betta( β )subunit
• A betta prime (β’) subunit
•A small omega (Ѡ) subunit
Core
enzyme
form
 RNA polymerase cannot start transcription by its
own it need a factor called sigma factor.
 It is a protein that allows specific binding of RNA
polymerase to promoter.
 RNA Polymerase core with this sigma factor is
called holoenzyme
 So complete RNA polymerase holoenzyme has 6
subunit.

4. PROMOTER REGION
It have RNA start point where the
transcription starts, That is the +1 position.
It have -10 region called the PRIBNOW BOX
followed by -35 region.
-10 region has sequence TATAAT
And -35 region has TTGACA sequence.
In these regions the RNA POLYMERASE
enzyme binds
-10 region has the function of transcription
initiation

5. PROKARYOTIC
TRANSCRIPTION
1.INITIATION
2.ELONGATION
3.TERMINATION

6. INITIATION
1. FORMATION OF CLOSED COMPLEX
RNA polymerase enzyme bind to the
promoter region.
DNA at this stage will be double stranded.
This complex is called the closed complex
2. FORMATION OF OPEN COMPLEX
DNA strand at the transcription start site
unwind to form an open complex.
When open complex are formed the enzyme
starts to add ribonucleotides ( rNTP’s) on the
template DNA.
 unlike DNA polymerase, RNA polymerase do
not need a primer to initiate transcription.

7. 3. ABORTIVE INITIATION
When the enzyme synthesize short RNA
molecule less than 10 base pair , it does
not further elongates which is called as
abortive initiation.
When the RNA Polymerase stabilizes
became able to copy 10 nucleotide or
more that will be called as successive
initiation. From here the elongation starts.

8. ELONGATION
When sigma factor is released RNA
POLYMERASE proceeds the process of
elongation.
The dissociation of sigma factor allows the core
polymerase enzyme to proceed along the DNA
template synthesising mRNA in the 5’ to 3’
direction at a rate of 40 nucleotide per second.

9. TERMINATION
When polymerase transcribe
the gene it must release the
transcribed product this process
is called termination
Termination takes place in two
modes
Rho independent
Rho dependent

10. RHO INDEPENDENT
•In rho independent termination no external
protein or external factor are required for
termination.
•Rho independent terminator also known as
intrinsic terminator.
•It consist of 2 sequence elements. Short inverted
repeats of 2 nucleotides followed by 8 A : T Rich
regions.
•RNA transcribe inverted repeated sequence and
the resulting RNA form a hairpin like structure by
base pairing with itself.
•The hairpin thus formed halt the RNA
polymerase enzyme.

11. RHO INDEPENDENT
The inverted repeats is further
followed by AT rich sequence
AT rich sequence after
transcription forms the new AU
Base pair the weakest of all the
base pair.
Because of this the RNA Is finally
releases ending the transcription

12. RHO DEPENDANT
It depends on protein called rho factor.
The rho protein bind to single stranded RNA Rich in
cytosine residues . These cytosine residues are also
known as rho utilization site .
When RNA polymerase reaches 100 nucleotide
away from the right side it stops the transcription .