Final answer:
The RNA polymerase most focused on in eukaryotes is RNA polymerase II, which transcribes all protein-coding nuclear pre-mRNAs. These pre-mRNAs are processed into mature mRNAs, which are essential for protein synthesis. This enzyme is key for eukaryotic gene expression due to the complexity and regulation needed in these cells.
Step-by-step explanation:
In eukaryotic cells, there are different types of RNA polymerase enzymes that specialize in transcribing different forms of RNA. The enzyme RNA polymerase II (RNAP II) is particularly important because it synthesizes all protein-coding nuclear pre-mRNAs. These pre-mRNAs undergo extensive processing after transcription but before translation to become mature mRNAs that are ready for translation into proteins.
Unlike bacteria like E.coli, which use a single RNA polymerase for all RNA synthesis, eukaryotes have multiple RNA polymerases. RNA polymerase I is responsible for transcribing ribosomal RNA (rRNA), RNA polymerase II transcribes messenger RNA (mRNA), and RNA polymerase III deals with transfer RNA (tRNA) and some other small RNAs. It's noteworthy that mRNAs are initially synthesized as longer pre-mRNAs and must be processed to become the mature forms that can exit the nucleus and be used for protein synthesis.
Eukaryotic mRNA is significantly more stable than bacterial mRNA. For instance, eukaryotic mRNAs can last for several hours, contributing to the complex regulation of gene expression in these organisms. The intricate process involved in eukaryotic transcription reflects the complexity and the regulated nature of gene expression in these cells.