RNA polymerase II

Definition

RNA polymerase II is the enzyme responsible for the transcription of protein-coding genes in eukaryotic cells. It is a multi-subunit complex that synthesizes messenger RNA (mRNA) from a DNA template, which is then used as a blueprint for protein synthesis.

5 Must Know Facts For Your Next Test

1. RNA polymerase II is the most complex of the three eukaryotic RNA polymerases, with 12 subunits that work together to transcribe protein-coding genes.
2. The enzyme recognizes and binds to specific DNA sequences called promoters, which mark the start of a gene, and then proceeds to synthesize the complementary mRNA strand.
3. RNA polymerase II is regulated by various transcription factors and epigenetic modifications, which can either activate or repress its activity, thereby controlling gene expression.
4. The enzyme has a specialized C-terminal domain (CTD) that is involved in the recruitment of factors necessary for mRNA processing, including capping, splicing, and polyadenylation.
5. Mutations or disruptions in the function of RNA polymerase II can lead to various human diseases, such as cancer, neurological disorders, and developmental abnormalities.

Review Questions

• Describe the role of RNA polymerase II in the process of transcription.
  • RNA polymerase II is the central enzyme responsible for the transcription of protein-coding genes in eukaryotic cells. It recognizes specific DNA sequences called promoters, which mark the start of a gene, and then proceeds to synthesize a complementary mRNA strand from the DNA template. The mRNA produced by RNA polymerase II is then used as a blueprint for the translation of proteins, which are the functional molecules that carry out the majority of cellular activities.
• Explain how the regulation of RNA polymerase II activity can impact gene expression.
  • The activity of RNA polymerase II is tightly regulated by various transcription factors and epigenetic modifications. These regulatory mechanisms can either activate or repress the enzyme's ability to transcribe genes, thereby controlling the expression of specific genes in a cell. For example, the recruitment of transcriptional activators can enhance RNA polymerase II's binding to promoters and increase the rate of transcription, while the binding of repressors can inhibit the enzyme's activity and reduce gene expression. The regulation of RNA polymerase II is crucial for coordinating the expression of genes involved in cellular processes, development, and disease states.
• Analyze the significance of the C-terminal domain (CTD) of RNA polymerase II and its role in mRNA processing.
  • The C-terminal domain (CTD) of RNA polymerase II is a unique feature that distinguishes it from the other eukaryotic RNA polymerases. The CTD is involved in the recruitment of various factors necessary for the processing of the newly synthesized mRNA, including capping, splicing, and polyadenylation. These mRNA processing steps are essential for the stability, localization, and translation of the mRNA molecule. By coordinating the transcription and processing of mRNA, the CTD of RNA polymerase II ensures the production of mature, functional mRNA that can be effectively utilized by the cell's protein synthesis machinery. The importance of the CTD highlights the multifunctional nature of RNA polymerase II and its central role in gene expression.

Related terms

Transcription:

The process of creating a complementary RNA copy of a sequence of DNA, which is the first step in gene expression.

Eukaryotic Cells: Cells that have a true nucleus and membrane-bound organelles, such as plant and animal cells.

Messenger RNA (mRNA): A single-stranded RNA molecule that carries the genetic information from the nucleus to the ribosomes, where it is used as a template for protein synthesis.