Process Of Transcription

Transcription has three phase of process that we know for the general knowledge as a biochemistry student. The three phase of transcription are:

• Chain Initiation (First Phase)
• Chain Elongation (Second Phase)
• Chain Termination (Third Phase)

Chain Initiation

Chain initiation is the first phase of transcription. This phase will begin when RNA polymerase binds to the promoter and forms closed complex. What is a promoter? A promoter is a DNA sequence that provides direction for DNA polymerase. Promoters can be about 100–1000 base pairs long. After that, DNA unwinds at promoter to form an open complex, which is required for the chain initiation.

After the first bond is synthesis, the RNA polymerase must escape the promoter. The process of the promoter escape is called as DNA scrunching, providing the energy needed to break interactions between RNA polymerase holoenzyme and the promoter.

Chain Elongation

The second phase of transcription is chain elongation. After the strands have been separated, transcription bubbles move down the DNA sequence to be transcribed. RNA polymerase catalyzes the formation of phosphodiester bond between the incrorp. ribonucleotides. Topoisomerases relax supercoils in front and behind the transcription bubble.

Chain Termination

Chain Termination is the last phase of the transcription. There are two types of termination mechanisms which are:

Intrinsic Termination: controlled by specific sequences
Termination involves "rho" protein: Rho-dependent sequences cause hairpin loop to form.
When the hairpin forms, the mechanical stress breaks the weak rU-dA bonds, now filling the DNA–RNA hybrid. This pulls the poly-U transcript out of the active site of the RNA polymerase, terminating transcription. In the "Rho-dependent" type of termination, a protein factor called "Rho" destabilizes the interaction between the template and the mRNA, thus releasing the newly synthesized mRNA from the elongation complex