The influence of hairpin RNA against lawc on the expression of overlapping lawc and Trf2 genes in D. melanogaster. Olga B. Simonova, Roman O. Cherezov, Julia E. Vorontsova, Ilya B. Mertsalov, Dina A. Kulikova. Genetics of Morphogenesis, Koltzov Institute of Developmental Biology, Moscow, Russian Federation.

   Two Drosophila genes - leg-aristae-wing complex (lawc) and TBP related factor 2 (Trf2) - share exonic overlap and are in opposite chromosomal orientation. We used genetic system of lawc/Trf2 gene complex as convenient model for in vivo researching the relationship between sense transcripts and the complementary antisense transcripts of the overlapping genes that regulate development in Drosophila. In order to investigate the interaction of sense and antisense transcripts we have tried to suppress an expression of the antisense lawc-transcripts using the method of RNA-interference gene inactivation. The transgenic constructions that express long hairpin RNA that subsequently cleaved into siRNAs and are capable to induce a knock-down of the antisense lawc-transcripts have been created and Drosophila transgenic lines have been finally generated. The activation of constructions in vivo in two-component UAS/GAL4 system led to fly death with high frequency. The comparative analysis of lawc and Trf2 gene expression has yielded unexpected result: level of an expression of the antisense lawc-transcripts in the conditions of their suppression has increased 3 times while level of Trf2 gene expression, on the contrary, has been down-regulated 4 times. Ectopic expression of Trf2 cDNA rescues lawc RNAi-induced lethality and have confirmed result. We concluded that sense and antisense lawc/Trf2 transcripts are discordant self-regulated. Data obtained showed that the RNAi of one of overlapping genes may cause a boomerang effect. This fact is very important for considering, as the list of human and vertebrates overlapping genes continually enlarged, and as it is predicted, "switch of" genes by using of the RNAi becomes one of approaches to treatment of some genetic diseases.