EXCISIONS OF THE IKIRARA1 TRANSPOSON IN AN ANOPHELES-GAMBIAE CELL-LINE

In order to determine whether there are active genomic copies of the A nopheles gambiae transposon Ikirara, we developed an excision assay ba sed on an internally deleted copy, Ikirara1, This element has 216 bp p erfect inverted repeats at its termini, apparently caused a duplicatio n of the dinucleotide TA at its insertion site between vitellogenin ge nes, and is thought to have been inserted recently at this location. T he firefly luciferase gene on the E. coli tac promoter was inserted in to Ikirara1 and used as a reporter to assess whether activities in an A. gambiae cell line could cause Ikirara excision, Excisions were obse rved at a rate of 0.038% in these experiments, but none was detected i n controls. The five independent excision products examined gave ident ical sequences. Excisions were nearly precise, but left behind a footp rint of 15 bp of the 3' inverted repeat of Ikirara1 between duplicated TAs. These excisions can be explained by a mechanism formally similar to that proposed for excision of mariner/Tc1 elements with cuts at th e transposon ends staggered by 15 bases.