Solution conformations of early intermediates in Mos1 transposition

Area of Science:

• Molecular Biology
• Genetics
• Structural Biology

Background:

• DNA transposases mediate genome rearrangements through a cut-and-paste mechanism.
• Transposition involves ordered nucleoprotein complexes that manage transposon end pairing, cleavage, and integration.
• Transposase binding to specific inverted repeat sequences at transposon ends initiates transposition.

Purpose of the Study:

• To determine the solution conformations and stoichiometries of DNA-free Mos1 transposase and Mos1 bound to a single transposon end.
• To elucidate the structural basis for Mos1 transposase dimerization and its conformational changes during transposition initiation.

Main Methods:

• Solution scattering techniques (e.g., Small-Angle X-ray Scattering).
• Biochemical assays to study protein-DNA interactions and complex formation.
• Analysis of protein structure and stoichiometry.

Main Results:

• Mos1 transposase exists as an elongated homodimer in the absence of DNA.
• The N-terminal 55 residues, including a helix-turn-helix motif, are essential for Mos1 dimerization.
• Mos1 remains elongated when bound to a single transposon end, with DNA primarily interacting with one monomer.
• This structure contrasts with the compact, crossed architecture of the dimer in the Mos1 paired-end complex (PEC).

Conclusions:

• Mos1 transposase undergoes significant conformational changes between its DNA-free state, single-end bound state, and paired-end complex.
• A conformational shift in the single-end complex, involving rotation and binding of the second transposon end, is proposed to facilitate PEC assembly.
• Understanding these structural dynamics is crucial for deciphering the mechanism of DNA transposition.