RNA polymerase II

RNA polymerase II (RNAP II, also known as POLR2 or RPB1) is an enzyme found in eukaryotic cells. It is responsible for transcribing DNA into messenger RNA (mRNA), a critical step in the process of gene expression. This enzyme is essential for the synthesis of mRNA and plays a pivotal role in the regulation of gene expression, making it a key player in cellular function and development.

Structure

RNA polymerase II is a complex molecule composed of 12 subunits, designated as RPB1 through RPB12. The largest subunit, RPB1, contains a unique carboxy-terminal domain (CTD) that is heavily phosphorylated during the transcription process. This phosphorylation is crucial for the enzyme's activity and its interaction with various transcription factors and RNA processing enzymes.

Function

The primary function of RNA polymerase II is to transcribe DNA into pre-mRNA. This process involves the unwinding of the DNA helix, the synthesis of RNA using one of the DNA strands as a template, and the eventual re-winding of the DNA. RNA polymerase II is also involved in the processing of pre-mRNA, which includes 5' capping, splicing, and 3' polyadenylation, processes that are essential for the maturation of mRNA.

Regulation

The activity of RNA polymerase II is tightly regulated through various mechanisms. These include the phosphorylation of the CTD, the interaction with transcription factors and mediator complexes, and the response to cellular signals. Such regulation ensures that genes are expressed at the right time, in the right cell type, and in response to the cellular environment.

Clinical Significance

Mutations in the genes encoding the subunits of RNA polymerase II can lead to a variety of diseases, including cancers and developmental disorders. Given its central role in gene expression, RNA polymerase II is also a target for certain toxins and drugs that aim to inhibit its activity, thereby controlling disease progression or pathogens that rely on host transcription machinery.

Research and Applications

Research on RNA polymerase II has provided insights into the fundamental processes of gene expression and regulation. It has also led to the development of novel therapeutic strategies, including the design of drugs that specifically target the transcription machinery in diseases such as cancer.

See Also

• Gene expression
• Transcription
• RNA polymerase
• Messenger RNA

References

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  Eukaryotic RNA polymerase II structure 1WCM
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  Alpha-Amanitin–RNA polymerase II complex 1K83