Transcription bubble

A molecular structure involved in the transcription of DNA to RNA

Transcription bubble is a molecular structure formed during the process of transcription when a limited portion of the DNA double helix is unwound. This unwinding allows the RNA polymerase to access the template strand of the DNA to synthesize RNA.

Formation

The transcription bubble is initiated when the RNA polymerase binds to the promoter region of the DNA. The enzyme then unwinds a short segment of the DNA, creating a bubble-like structure. This unwound region typically spans about 12-14 base pairs.

Function

Within the transcription bubble, the RNA polymerase reads the template strand of the DNA and synthesizes a complementary RNA strand. The bubble moves along the DNA as transcription proceeds, with the DNA ahead of the bubble being unwound and the DNA behind the bubble re-annealing.

Structure

The transcription bubble consists of the RNA polymerase, the unwound DNA, and the nascent RNA strand. The DNA within the bubble is separated into two strands: the template strand, which is read by the RNA polymerase, and the non-template strand.

Role in Transcription

The transcription bubble is crucial for the accurate synthesis of RNA. It ensures that the RNA polymerase can access the DNA template strand and that the correct RNA sequence is produced. The bubble also helps to stabilize the transcription complex and facilitates the movement of the RNA polymerase along the DNA.

Termination

Once the RNA polymerase reaches a termination signal on the DNA, the transcription bubble collapses, and the newly synthesized RNA is released. The DNA strands re-anneal, and the RNA polymerase dissociates from the DNA.

Related pages

• RNA polymerase
• Transcription (biology)
• DNA replication

References

• Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2002). Molecular Biology of the Cell. 4th edition. New York: Garland Science.
• Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D., & Darnell, J. (2000). Molecular Cell Biology. 4th edition. New York: W. H. Freeman.

Illustration of a transcription bubble showing the unwound DNA and the RNA polymerase.

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