Assembly of the mariner Mos1 synaptic complex.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Transposable elements (TEs) mobilize via a cut-and-paste mechanism.
• This process relies on a nucleoprotein complex called the synaptic complex.
• Understanding TE mobility is crucial for genome stability and evolution.

Purpose of the Study:

• To elucidate the structure and assembly of the Mos1 synaptic complex.
• To identify the molecular interactions between Mos1 transposase and its DNA substrate.
• To understand the mechanism of Mos1 transposition initiation.

Main Methods:

• Biochemical assays to study protein-DNA interactions.
• Electrophoretic mobility shift assays (EMSAs) to detect complex formation.
• Analysis of Mos1 inverted terminal repeat sequences for binding motifs.

Main Results:

• The Mos1 synaptic complex (PEC2) involves a transposase tetramer binding to two inverted terminal repeats.
• A simpler complex (SEC2) forms first, with two transposase molecules binding one terminal repeat.
• Two distinct transposase binding sites exist within a single Mos1 terminal repeat, featuring palindromic and mirror motifs.
• Mos1 transposase dimer formation within a terminal repeat occurs cooperatively.
• The tetrameric structure explains the transposase's inability to bind both repeat and target DNA simultaneously.

Conclusions:

• The Mos1 synaptic complex assembly is a stepwise process involving SEC2 and PEC2 intermediates.
• The structure of Mos1 inverted terminal repeats facilitates cooperative binding of transposase dimers.
• This mechanism ensures precise recognition and binding of the transposase to its cognate DNA elements for transposition.