Steps in Transcription | The University Of Western Ontario

University:
The University Of Western Ontario
Course:
Biology 2290F | Scientific Method in Biology
Academic year:

2022
Views:

314

Pages:

5
Author:

Kyuwon J.

Steps in transcription Initiation 1. RNAP holoenzyme binds to the promoter ● Sigma had recognized but still did not open up the double stranded DNA 2. RNA polymerase unwinds the DNA strands around the start site- open complex ● When closely in contracted with promoter the DNA get unwind and get open complex 3. The first NTP is brought to the template base pairing with the base at +1 ● No primer is required ● RNA polymerase could bring in NTP and being making transcripts 4. Using ATP,GTP,CTP and UTP as substrates, chain elongation proceeds in 5`=>3` direction, following paring rules ● Would be using UTP since it is RNA that is being synthesized, so no need for TTP Transcription-RNA Polymerase with bound DNA and RNA RNA synthesis ● Phosphodiester bonds form-pyrophosphate is released ● This is a spontaneous process because phosphates are being released ● Notice that this is a process of RNA synthesis, by looking at OH on the 2` position. ○ In case of DNA, only have H on the 2` position as its a ‘deoxyribose’ ○ The RNA would have OH since its ribose 5. After addition of 5-10 nucleotide, sigma falls off the holoenzyme ● This sigma subunits is moved for new synthesis ○ Could bind to other holoenzyme to bind to -35, and -10 sites 6. The transcription bubble moves downstream (5`~3`) with the template DNA reannealing behind 7. RNA synthesis proceeds until a terminator is reached and RNA polymerase falls off 8. Sigma rebinds RNAP and the cycle is repeated Mechanisms for transcription termination in Prokaryotes ● In bacteria, there are two types ○ Rho- independent or intrinsic termination ■ Sequence and secondary structure ○ Rho- dependent ■ Use of ATP