University:
Swansea University
Course:
PM-133 | Evolutionary and Molecular Genetics
Academic year:

2023
Views:

75

Pages:

3
Author:

Amal J.

Models proposed for abortive transcription 1) Transient excursion - simply leave 2) inchworm model - elastic action and pulling of core by 3) scrunching Termination: 1) Rho dependent 2) Rho independent Rho independent (intrinsic termination) → termination signal • palindromic GC rich sequence followed by AT rich region, transcript is self complementary →stem and loop structure is formed because of the presence of palindromes, stem and loop inhibits the bond b/w RN & DNA, followed by a string of uracil and this RNA displaced from transcription bubble, without RNA core enzyme which has low affinity to DNA and core detach reason for abortive transcription, core alone has less affinity to DNA only. RNApol: 1) RNTP entry channel 2) DNA entry channel (template, N-template) 3) DNA exit channel 4) RNA exit channel → Initiate polymerization without RNA primer → A to first position → RNApol active site closed with 1.7 domain → mRNA exit channel is usually blocked by 3rd & 4th high region of the σ unit, this acts as a gate; the pressure of around 10 nucleotides push the blocking region and come out → If σ doesn’t detach after 8-10 nucleotides, the whole polymerase will detach • Abortive transcription: if the enzyme synthesize short RNA molecules of less than 10 bp, it does not further elongates which is called abortive initiation. • After 10 bp completion, transcription continues without interruption (elongation) upto 10th initiation after that elongation.