During Dmau\mariner transposon DNA cleavage by Dmau\mariner\T : the nontransferred strand is cleaved initially; first strand cleavage is not tightly coupled to second strand cleavage and can occur independently of synapsis; and second strand cleavage of mariner does not occur via a hairpin intermediate.

The ITR binding domain of Dmau\mariner\T has been localised between amino acids 1 and 141.

Dmau\mariner\T encodes a transposase which excises Dmau\mariner\T from plasmid DNA in vitro. The transposase recognises the inverted repeats at the end of Dmau\mariner\T in a sequence specific manner via a DNA binding domain located within the N-terminal 120 amino acids. It binds the right hand inverted repeat about five times more strongly than the left. Dmau\mariner\T transposase monomers bind to each other. Mutations along the length of the Dmau\mariner\T transposase protein reduce the monomer interaction, indicating that no single protein-protein interaction domain is involved.

Dmau\mariner transposase seems to distinguish between the 5' and 3' ends of the Dmau\mariner element. Mutations in the 5' inverted repeat are smaller and more frequent than in the 3' terminal repeat, but secondary mutations in elements with a previous 5' lesion tend to have 3' lesions resembling those normally found at the 5' end.

The Dmau\w^pch mosaicism screen efficiently reveals mutations in the Dmau\mariner\T that are defective in the excision reaction of transposition. Site-directed and EMS induced transposase mutations demonstrate that the D,D(34)D domain cannot be replaced with D,D(34)E domain, identify various essential residues in the transposase and indicate that the majority of hypomorphic transposase mutations impair the activity of the wild-type transposase.

Genetic studies of the Mos1 transposase suggest two distinct types of regulatory mechanism: overproduction inhibition, OPI (in which excessive quantities of the wild type transposase significantly reduce overall frequency of excision of a target Dmau\mariner element) and dominant negative complementation, DNC (which is observed in a significant proportion of hypomorphic mutations in the transposase.

Genetic and biochemical studies have identified a point mutation in the transposase that shows significant dominant-negative complementation when heterozygous with a wild type coding sequence; this finding suggests that the transposase functions as an oligomer. Application of the yeast two hybrid system implies the transposase consists of subunits that interact. Elevated expression of transposase above a certain threshold decreases the frequency of excision of a mariner target element. Therefore overproduction of transposase may serve as one mechanism by which transposition is regulated.

PCR amplification provided regions of presumed transposase genes from D.mauritiana and 10 other insects representing 6 additional orders. Sequence analysis revealed a diverse array of mariner elements, with multiple subfamilies, indicating vertical inheritance and horizontal transfer.