A 3.5-kb segment of DNA containing the complete sequence of a mouse gene is available. The DNA segment contains the promoter sequence and extends beyond the polyadenylation site of the gene. The DNA is studied by band shift assay (see Research Technique 8.1), and the following gel bands are observed. Match these conditions to a specific lane of the gel. 3.5-kb fragment plus TFIIB and TFIID

Key Concepts

Promoter Sequence

The promoter sequence is a region of DNA located upstream of a gene that initiates transcription. It serves as the binding site for RNA polymerase and transcription factors, which are essential for the transcription of the gene into mRNA. Understanding the promoter's role is crucial for analyzing gene expression and the effects of regulatory proteins.

TFIIB and TFIID

TFIIB and TFIID are essential transcription factors involved in the initiation of transcription in eukaryotic cells. TFIID binds to the promoter region and helps recruit RNA polymerase II, while TFIIB stabilizes the interaction between TFIID and RNA polymerase. Their presence in the band shift assay indicates the formation of a transcription complex, which is critical for understanding gene regulation.

Band Shift Assay

A band shift assay, also known as an electrophoretic mobility shift assay (EMSA), is a technique used to study protein-DNA interactions. In this assay, DNA fragments bound to proteins migrate more slowly through a gel than unbound DNA, resulting in distinct bands. This method allows researchers to identify specific proteins that interact with DNA sequences, providing insights into gene regulation mechanisms.