Structural basis of Ets1 activation by Runx1

Area of Science:

• Molecular Biology
• Structural Biology
• Hematopoiesis

Background:

• Runx1 is crucial for definitive hematopoiesis and is implicated in leukemia development.
• Runx1 regulates gene expression through activation of Ets1 on composite DNA elements.
• The structural basis for Ets1 activation by Runx1 has not been elucidated.

Purpose of the Study:

• To determine the crystal structure of the Runx1-Ets1-DNA complex.
• To elucidate the structural mechanism of Ets1 activation by Runx1.
• To investigate the role of direct Ets1•Runx1 interaction in transcriptional regulation.

Main Methods:

• X-ray crystallography of the ternary complex (Runx1, Ets1, TCRα enhancer DNA).
• Structure-guided mutagenesis of Runx1.
• DNA-binding and transcriptional assays.

Main Results:

• The crystal structure revealed Runx1 binding to Ets1's DNA-binding domain, displacing an autoinhibitory module.
• This interaction represents a novel mechanism for Ets1 activation.
• Mutational studies confirmed the critical role of direct Ets1•Runx1 interaction in activating both wild-type and phosphorylated Ets1.

Conclusions:

• Direct interaction between Runx1 and Ets1 is essential for Ets1 activation.
• This mechanism explains how Runx1 effectively activates Ets1, including inhibited forms.
• Findings provide insights into the regulation of hematopoiesis and potential therapeutic targets in leukemia.