Molecular basis for transposase activation by a dedicated AAA+ ATPase

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Transposases mediate essential genetic processes like chromosomal rearrangements and gene dissemination.
• Many transposases require AAA+ ATPase subunits for regulated function, but mechanisms remain unclear.

Purpose of the Study:

• To elucidate the mechanism by which the IstB AAA+ ATPase regulates the IS21 transposase (IstA).
• To understand how ATPase activity controls DNA binding, transposase recruitment, and catalytic activation.

Main Methods:

• Utilized solution and cryogenic electron microscopy (cryo-EM) to determine the structure of the transpososome complex.
• Investigated the self-assembly of the IstB ATPase and its interaction with target DNA and IstA.

Main Results:

• The IstB ATPase forms a pentamer of dimers, inducing significant curvature in target DNA.
• Dimerization of IstB decamers creates an S-shaped DNA configuration, recruiting IstA to form a ~1 MDa transpososome.
• Nucleotide-dependent conformational changes in IstA are triggered at the IstB-IstA interface, activating DNA strand transfer.

Conclusions:

• AAA+ ATPase regulators remodel DNA and transposases through nucleotide-controlled assembly and DNA deformation.
• This mechanism explains how regulators ensure site selectivity and catalytic activation in diverse transposition systems like Tn7, Mu, and CRISPR-associated elements.