For a eukaryotic gene whose transcription requires the activity of an enhancer sequence, explain how proteins bound at the enhancer interact with RNA pol II and transcription factors bound at the promoter.

Verified step by step guidance

1. span>Identify the location of the enhancer sequence relative to the promoter. Enhancers can be located upstream, downstream, or even within introns of the gene they regulate.
2. span>Understand that proteins called transcription factors bind to the enhancer sequence. These proteins are often referred to as activators.
3. span>Recognize that the DNA between the enhancer and the promoter loops out, allowing the enhancer-bound proteins to come into close proximity with the promoter-bound proteins and RNA polymerase II.
4. span>Learn that the enhancer-bound activators interact with coactivators or mediator complexes, which serve as a bridge to RNA polymerase II and the general transcription factors at the promoter.
5. span>Realize that these interactions facilitate the assembly of the transcriptional machinery at the promoter, enhancing the rate of transcription initiation by RNA polymerase II.

Key Concepts

Enhancer Sequences

Enhancer sequences are regulatory DNA elements that can significantly increase the transcription of associated genes. They are typically located far from the promoter region and can function in a tissue-specific manner. Enhancers bind transcription factors, which then interact with the transcription machinery, facilitating the recruitment of RNA polymerase II (RNA pol II) to initiate transcription.

Transcription Factors

Transcription factors are proteins that bind to specific DNA sequences to regulate gene expression. They can act as activators or repressors, influencing the assembly of the transcriptional machinery at the promoter. In the context of enhancers, transcription factors bound to these elements can form loops in the DNA, bringing them into proximity with RNA pol II and other factors at the promoter, thereby enhancing transcription.

RNA Polymerase II (RNA pol II)

RNA polymerase II is the enzyme responsible for synthesizing mRNA from a DNA template during transcription in eukaryotic cells. It requires the assembly of various transcription factors and co-activators at the promoter to initiate transcription. The interaction between RNA pol II and proteins bound at enhancers is crucial for the efficient transcription of genes, as these interactions help stabilize the transcription complex and promote the transition from initiation to elongation.