UC Irvine

Long terminal repeat (LTR) retrotransposons have been identified in a wide variety of organisms including fungi (Boeke and Sandmeyer 1991), plants (Voytas and Ausubel 1988; Flavell et al. 1995; Smyth et al. 1989; Grandbastien et al. 1989), invertebrates (Springer et al. 1991; Britten 1995; Bingham and Zachar 1989), and vertebrates (Flavell and Smith 1992). Many of these LTR retrotransposons can be sorted into two superfamilies named after the prototypic Drosophila elements copia and gypsy (mdg4). The early history of the characterization of these elements has been reviewed elsewhere (Boeke and Corces 1995; Bingham and Zachar 1989). Expression of representative elements results in the formation of intracellular particles analogous to the retroviral core particle. This review will focus on morphogenesis of that particle — assembly, processing, and reverse transcription — in members of these families for which the DNA sequence has been determined in the fruit fly Drosophila and in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces Pombe. Collectively, these systems reveal tremendous diversity as well as striking similarities among the mechanisms members of these two LTR retrotransposon families and retroviruses have used to solve common morphogenetic problems.