Abstract
Genetic studies of the mariner transposable element Mos1 have revealed two novel types of regulatory mechanisms. In one mechanism, overproduction of the wild-type transposase reduces the overall level of transposase activity as assayed by the excision of a nonautonomous mariner target element. This mechanism is termed overproduction inhibition (OPI). Another mechanism is observed in a class of hypomorphic missense mutations in the transposase. In the presence of wild-type Mos1 transposase, these mutations exhibit dominant-negative complementation (DNC) that antagonizes the activity of the wild-type transposase. We propose that these regulatory mechanisms act at the level of the transposase protein subunits by promoting the assembly of oligomeric forms, or of mixed-subunit oligomers, that have reduced activity. We suggest that these regulatory mechanisms may apply generally to mariner-like elements (MLEs). Overproduction inhibition may help explain why the MLE copy number reaches very different levels in different species. Dominant-negative complementation may help explain why most naturally occurring copies of MLEs have been mutationally inactivated.
