RNA polymerase II is an essential enzyme involved in the process of transcription, which is the synthesis of RNA molecules from DNA templates. Specifically, it is responsible for transcribing protein-coding genes, also known as messenger RNA (mRNA), and some non-coding RNA genes in eukaryotic organisms. This enzyme is the primary RNA polymerase found in the nucleus of eukaryotic cells.
RNA polymerase II consists of several subunits that work collaboratively to perform transcription. These subunits include the catalytic core enzyme, which is responsible for elongating the RNA molecule, and various accessory proteins called transcription factors. Together, they form the RNA polymerase II transcription initiation complex, which is required for the proper initiation and regulation of transcription.
The process of transcription by RNA polymerase II occurs in multiple stages, including initiation, elongation, and termination. During initiation, the RNA polymerase II binds to the DNA promoter region upstream of the target gene. Next, it unwinds the DNA molecule and begins synthesizing the RNA transcript in the 5' to 3' direction. Elongation involves the continuous addition of ribonucleotides to the growing RNA molecule, guided by the complementary base pairing with the DNA template strand. Finally, termination signals lead to the dissociation of RNA polymerase II from the DNA template and the release of the synthesized RNA transcript.
Overall, RNA polymerase II plays a critical role in gene expression by synthesizing messenger RNA molecules, which carry the genetic information from the DNA to the ribosomes for protein synthesis.
