Final answer:
The efficient initiation of transcription by RNA polymerase II in eukaryotes involves upstream promoter sequences, primarily represented by a TATA box. TATA-binding protein (TBP) binds to the TATA box to begin the formation of the transcription initiation complex.
Step-by-step explanation:
Eukaryotic Transcription Initiation by RNA Polymerase II
Regarding the efficient initiation of transcription by RNA polymerase II in eukaryotes, specific upstream signals involved are promoters. A typical eukaryotic promoter contains a TATA box sequence motif located approximately 25-35 nucleotides upstream from the transcription start site. The TATA box, an A-T rich sequence, facilitates the unwinding of DNA to allow transcription to begin. Essential to this process, a protein known as the TATA-binding protein (TBP), part of the larger transcription factor TFIID, initially binds to this TATA box.
While promoters for genes transcribed by RNA polymerases I and III also contain upstream signals, their conserved promoter sequences differ from those utilized by RNA polymerase II. Specifically, RNA polymerase I transcribes genes with GC-rich promoter sequences, while RNA polymerase III may have promoters within the genes themselves. For RNA polymerase II, it's these intricate promoter sequences, mainly located just upstream of the genes they regulate, that are crucial for initiating transcription.