Lentiviral Packaging Protocol
Scientists use lentiviral vectors to genetically engineer cells. As modified lentivirus, instead of delivering their own genetic information when they infect a cell, they deliver a gene of interest that becomes a part of the cellular DNA, expressed by the cell.
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Lentivirus
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When lentivirus genes integrate into the cell's DNA, the cell produces proteins for making more virus particles. These viral proteins self-assemble and become viral capsids -- the outer virus shell. The cell also makes a piece of RNA that contains the genes necessary for making more viral particles. This RNA has a special packaging sequence that particle proteins recognize and package inside the capsid. The particles exit the cells, infect new cells and repeat the cycle.
Packaging
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Scientists use this packaging process to trick modified virus particles into packaging a gene of interest, such as green fluorescent protein (GFP). They create a piece of DNA -- a plasmid -- containing only the packaging signal and the GFP gene. Separate plasmids contain genes for making more particles.
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Transfection
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Plasmids mixed in a lipid or salt solution are placed on cells that absorb DNA and make virus particles for collection from the growth medium. The particles, which only contain the gene sequence for GFP, can infect other cells that then express GFP. Those cells didn't receive genes for making more viruses, however, so no viral replication occurs.
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