A simple method for the rapid purification of copia virus-like particles from Drosophila Schneider 2 cells

Drosophila retrotransposon copia produces virus-like particles (VLPs) in cultured Drosophila cells. The VLPs contain copia RNA and reverse transcriptase activity, and thus, play a major role in copia replication. Here, we report a rapid and simple method for the purification of copia VLPs from Drosophila Schneider 2 (S2) cells. The VLP purification procedure consists of a series of short centrifugation steps and eliminates the tedious and time-consuming performance of sucrose, metrizamide and cesium chloride (CsCl) gradients. The purity and presence of VLPs at different purification steps was monitored by transmission electron microscopy (TEM), immunochemical detection methods, and by Northern blot analysis. In addition to providing a fast protocol for VLP purification, our results also show that copia particles are mainly located in the nucleus of S2 cells. This new protocol may find broad applications for the purification of various other VLPs, and thus, may be of great value to other investigators with similar interests.