RNA polymerase II is an essential enzyme found in eukaryotic cells that plays a crucial role in the process of transcription. It synthesizes messenger RNA (mRNA) by reading the DNA template and linking together ribonucleotides in a sequence that corresponds to the gene being expressed. This process is vital for converting genetic information into proteins. In addition to mRNA, RNA polymerase II also produces small nuclear RNAs (snRNAs) and microRNAs (miRNAs), which are important for gene regulation and RNA processing. The activity of RNA polymerase II is tightly regulated by various transcription factors and co-factors, ensuring that genes are expressed at the right time and in the right amounts.