HETEROLOGOUS INDUCTION OF TY1 RETROTRANSP OSITION - REVERSE-TRANSCRIPTASE PLAYS THE CENTRAL ROLE IN INITIATION OF THE RETROTRANSPOSITION CYCLE

A new method was developed to study the mechanism of initiation of the retrotransposition cycle: retrotransposons of Drosophila melanogaster , gypsy, copia, and 17.6 were expressed in yeast under the control of potent yeast promoters. Expression of retrotransposons induced formati on of viruslike particles (VLPs) associated with full-length Ty1 RNA a nd DNA sequences. This phenomenon was termed heterologous induction. W hen the gene for reverse transcriptase of human immunodeficiency virus (HIV) was expressed in yeast, the same results were obtained, These d ata allowed us to assume the excess of active reverse transcriptase to play the central role in induction of transposition. Possible mechani sms of induction of Ty1 transposition by homologous and heterologous e lements are discussed.