Morphogenesis of the Ty3 viruslike particle.
Michael Aye (1), Pierre Baldi (2), Nadejda Beliakova-Bethell (1), Becky Irwin (1), Yimeng Dou (2), Min Zhang (1), Suzanne Sandmeyer (1)
(1) Biological Chemistry, University of California, University, Irvine, CA, 92697-1700, USA;
(2) Information and Computer Science
Ty3 is a retroviruslike element in Saccharomyces cerevisiae. Ty3 is comprised of long terminal repeats flanking an internal domain which contains two open reading frames, GAG3 and POL3. Expression of Ty3 results in assembly of viruslike particles and processing of Gag3 and Gag3-Pol3 precursors into mature capsid, nucleocapsid, protease, reverse transcriptase, and integrase. The sequences of these domains are homologous to their retrovirus counterparts and the proteins carry out related functions. Ty3 cDNA is produced in association with the retroviruslike particle, translocated into the nucleus, and integrated into chromosomal DNA. The major difference between Ty3 and simple retroviruses, such as Moloney murine leukemia virus, is that Ty3 does not have an obligatory extracellular phase in its cell cycle. During Ty3 particle morphogenesis, Ty3viruslike particles accumulate at a perinuclear location. Screening of the yeast knockout collection for genes that affect Ty3 transposition resulted in identification of genes encoding endosome to vacuole trafficking, vacuole inheritance, and nuclear pore proteins. The contribution of vesicular trafficking proteins to particle morphogenesis is of particular interest as these functions have been implicated in late stages of retroviral budding. Experiments are underway to determine the relationships among the functions of these yeast genes and Ty3 particle morphogenesis.
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