Explain the features of the Initiator (Inr) elements, BREs, DPEs, and MTEs of focused promoters.

Verified step by step guidance

1. Start by defining what a focused promoter is: a promoter type where transcription initiates at a single or a few closely spaced start sites, often found in genes with regulated expression.
2. Explain the Initiator (Inr) element: it is a core promoter sequence that overlaps the transcription start site (TSS) and helps direct the accurate initiation of transcription by RNA polymerase II. Typically, it has a consensus sequence around the +1 position.
3. Describe the BRE (TFIIB Recognition Element): this element is located immediately upstream or downstream of the TATA box and serves as a binding site for the transcription factor TFIIB, which helps recruit RNA polymerase II to the promoter.
4. Discuss the DPE (Downstream Promoter Element): found downstream of the TSS (around +28 to +32), the DPE works together with the Inr to facilitate transcription initiation, especially in promoters lacking a TATA box.
5. Explain the MTE (Motif Ten Element): located downstream of the TSS (around +18 to +27), the MTE cooperates with the Inr and DPE to enhance transcription efficiency by providing additional binding sites for transcription factors.

Key Concepts

Initiator (Inr) Element

The Initiator (Inr) is a core promoter element located around the transcription start site (TSS). It helps direct RNA polymerase II to the correct initiation point, often compensating for the absence of a TATA box. The Inr sequence is typically rich in pyrimidines and purines, facilitating precise transcription initiation.

TFIIB Recognition Elements (BREs)

BREs are short DNA sequences found immediately upstream (BREu) or downstream (BREd) of the TATA box in focused promoters. They serve as binding sites for the general transcription factor TFIIB, enhancing the stability and specificity of the pre-initiation complex formation, thus influencing transcription efficiency.

Downstream Promoter Elements (DPEs) and Motif Ten Elements (MTEs)

DPEs and MTEs are core promoter elements located downstream of the TSS, typically between +28 to +32 for DPE and +18 to +27 for MTE. They function in promoters lacking a TATA box by interacting with transcription factors like TFIID, aiding in the recruitment of RNA polymerase II and promoting accurate transcription initiation.