Final answer:
RNA polymerase II promoters are unusual because they include a TATA box, require a complex of transcription factors for binding, and lack inherent helicase activity, relying instead on the TFIIH protein.
Step-by-step explanation:
Promoters of RNA polymerase II are unusual because they contain a sequence called the TATA box, which is an A-T rich element known for its low thermostability, allowing the DNA template to locally unwind in preparation for transcription. This sequence is found at approximately -25 to -35 bases relative to the initiation site. Unlike promoters for RNA polymerase I and III, the RNA polymerase II promoter is associated with a complex of basal transcription factors, including TFIID which contains the TATA-binding protein (TBP). These transcription factors and the TBP specifically recognize the TATA box, facilitating the formation of the transcription initiation complex by RNA polymerase II.
The eukaryotic transcription initiation differs significantly from the prokaryotic process as it involves a myriad of transcription factors for RNA polymerase II binding. Unlike prokaryotic RNA polymerase which includes a helicase activity, the eukaryotic version relies on the TFIIH protein for helicase activity to help unwind DNA for transcription initiation. Complex promoter structures and the need for various transcription factors make the RNA polymerase II promoters highly intricate compared to their prokaryotic counterparts.