The DRIP complex and SRC-1/p160 coactivators share similar nuclear receptor binding determinants but constitute...

Area of Science:

• Molecular Biology
• Gene Regulation
• Biochemistry

Background:

• Transcriptional activation depends on chromatin access and transcription machinery interaction.
• The vitamin D receptor (VDR) interacts with coactivator complexes.
• DRIP (VDR-interacting proteins) is a novel coactivator complex identified previously.

Purpose of the Study:

• To characterize the nuclear receptor binding features of DRIP205, a subunit of the DRIP complex.
• To understand how DRIP205 interacts with nuclear receptors like VDR and thyroid hormone receptor.
• To investigate the distinct roles of coactivator complexes in transcriptional activation.

Main Methods:

• Utilizing the hormone-bound VDR ligand binding domain (LBD) as an affinity matrix.
• Characterizing the interaction of DRIP205 with nuclear receptors using LXXLL motifs and the AF-2 subdomain.
• Analyzing coactivator binding in nuclear extracts and assessing histone acetyltransferase activity.

Main Results:

• DRIP205 directly interacts with VDR and thyroid hormone receptor upon ligand binding, anchoring the DRIP complex.
• DRIP205 uses LXXLL motifs for nuclear receptor interaction, with both motifs crucial for VDR-DRIP complex function in vivo.
• DRIP complexes bind VDR LBD distinctly from p160 coactivators and lack histone acetyltransferase activity.

Conclusions:

• Distinct coactivator complexes, including DRIP and p160, bind to the same nuclear receptor transactivation region.
• These distinct complexes possess different functions and are both necessary for efficient transcription activation by nuclear receptors.
• DRIP205 plays a critical role in mediating the interaction of the DRIP complex with nuclear receptors.