Final answer:
A eukaryotic mRNA promoter for RNA polymerase II includes sequences like the TATA box located at -25 to -35, the CAAT box at about -80, and possibly GC-rich or octamer boxes further upstream. The promoter facilitates transcription initiation by forming an initiation complex with transcription factors and RNA Polymerase II.
Step-by-step explanation:
The structure of the eukaryotic mRNA promoter for RNA polymerase II transcription involves several critical sequences. The central part of the promoter is the TATA box, an A-T rich sequence that is recognized and bound by the TATA-binding protein (TBP) and other transcription initiation factors like TFIID. This is typically located around -25 to -35 bases upstream of the transcription start site. Beyond this, eukaryotic promoters may contain additional sequences like the CAAT box, which is usually found at approximately -80 bases, and can also include GC-rich sequences or octamer boxes further upstream.
The associative interactions among these promoter elements and transcription factors enable the formation of a eukaryotic initiation complex, which is vital for the commencement of transcription by RNA Polymerase II. The promoter, therefore, plays a crucial role in signaling where RNA Polymerase II should start transcribing the gene. The positioning of label '1' would be the promoter region, which contains elements such as the TATA box, CAAT box, and GC-rich sequences. Label '2' represents the transcription initiation site where the transcription of mRNA actually begins. These sequences are imperative for the regulation of gene expression as they dictate the affinity for transcription factors and ultimately the transcriptional activity of the gene.