Multiple DNA-binding modes for the ETS family transcription factor PU.1

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• ETS transcription factors bind DNA via a conserved ETS domain.
• The ETS member PU.1 exhibits unique DNA-binding properties, including sequential dimerization.

Purpose of the Study:

• To extensively characterize the site-specific PU.1 ETS complexes using spectroscopic and biochemical methods.
• To elucidate the mechanism and structural basis of PU.1 sequential dimerization at DNA-binding sites.

Main Methods:

• Titration calorimetry
• NMR spectroscopy
• Mutational analysis
• Hydroxyl radical DNA footprinting

Main Results:

• PU.1 requires flanking DNA bases beyond the core 5'-GGAA-3' site for sequential dimerization into a 2:1 complex.
• Mutational analysis identified a dimerization interface on PU.1 distal to the DNA.
• PU.1 dimers occupy an extended DNA footprint compared to monomers.
• Dimerization was not observed with the closely related Ets-1 ETS domain.

Conclusions:

• Sequential dimerization of PU.1 is dependent on DNA sequence and length.
• The distal surface of PU.1 mediates dimerization, suggesting an autoinhibitory mechanism.
• This dimerization behavior is specific to PU.1 and may not be conserved across all ETS factors.