Enzyme that facilitates opening of DNA helix during transcription: RNA polymerase

During transcription, the process by which genetic information in DNA is transcribed into RNA, the DNA helix needs to be opened to expose the template strand for RNA synthesis. This is facilitated by an enzyme called RNA polymerase.

Role of RNA polymerase
- RNA polymerase is responsible for catalyzing the synthesis of RNA from a DNA template during transcription.
- It recognizes specific DNA sequences, known as promoters, that mark the beginning of genes and binds to them, initiating the transcription process.
- Once RNA polymerase binds to the promoter region, it unwinds and separates the DNA double helix, creating a transcription bubble.
- The enzyme then moves along the DNA template strand, synthesizing an RNA molecule that is complementary to the DNA sequence.

Steps involved in opening the DNA helix during transcription:
1. Recognition of promoter: RNA polymerase recognizes specific promoter sequences on the DNA molecule, which signal the start of a gene. Promoters are usually located upstream of the gene sequence.

2. Binding of RNA polymerase: Once the promoter is recognized, RNA polymerase binds to it, forming a stable complex known as the closed complex. This binding occurs through interactions between the enzyme and the DNA backbone.

3. Unwinding of DNA helix: RNA polymerase, with the help of additional proteins called transcription factors, unwinds and separates the DNA double helix at the promoter region. This unwinding creates a transcription bubble, exposing the template strand for RNA synthesis.

4. Initiation of transcription: As the DNA helix unwinds, RNA polymerase initiates transcription by synthesizing an RNA molecule that is complementary to the DNA template strand. This process begins at the start site defined by the promoter sequence.

5. Elongation and termination: After the initiation of transcription, RNA polymerase continues to move along the DNA template strand, synthesizing the RNA molecule. Once the entire gene sequence is transcribed, the RNA polymerase reaches a termination signal, which marks the end of transcription.

In conclusion, RNA polymerase plays a crucial role in opening the DNA helix during transcription. It recognizes the promoter sequence, binds to it, and unwinds the DNA double helix, allowing for the synthesis of RNA from the DNA template strand.