PEGASUS, A SMALL TERMINAL INVERTED REPEAT TRANSPOSABLE ELEMENT FOUND IN THE WHITE GENE OF ANOPHELES-GAMBIAE

Pegasus, a novel transposable element, was discovered as a length poly morphism in the white gene of Anopheles gambiae. Sequence analysis rev ealed that this 535 bp element was flanked by 8 bp target site duplica tions and 8 bp perfect terminal inverted repeats similar to those foun d in many members of the Tc1 family. Its small size and lack of long o pen reading frames preclude protein coding capacity. Southern analysis and in situ hybridization to polytene chromosomes demonstrated that P egasus occurs in approximately 30 copies in the genomes of An. gambiae and its sibling species and is homogenous in structure but polymorphi c in chromosomal location. Characterization of five additional element s by sequencing revealed nucleotide identities of 95% to 99%. Of 30 Pe gasus-containing phage crones examined by PCR, only one contained an e lement exceeding 535 bp in length, due to the insertion of another tra nsposable element-like sequence. Thus, the majority, if not all, extan t Pegasus elements may be defective copies of a complete element whose contemporary existence in An. gambiae is uncertain. No Pegasus-hybrid izing sequences were detected in nine other anophelines and three culi cines examined, suggesting a very limited taxonomic distribution.