The HIV virus is tricky. It uses the machinery in human cells to reproduce and mutates so fast that neither our immune system nor antiviral drugs can get a good hold on it. But, so some scientist thought, what if we can use these characteristics to our advantage?
A recent study details how researchers have been able to co-opt HIV’s replication machinery and its capability to introduce new genes in human cells to develop a system (called Retrovolution) for generating lots of potentially useful gene variants.
They developed a vector based on the HIV virus to insert the gene they wanted to mutate, the gene for the dCK protein, which is involved in the activation of cancer drugs, into the DNA of so-called producer cells (in this case, human embryonic kidney cells, but they can basically be any type of mammalian cell). Through mimicking successive infection cycles, mutations readily arose, eventually leading to a ‘library’ of mutant genes.
When many gene variants had been produced this way, the proteins they code for could be screened. Here, the dCK protein variants were expressed in tumor cells which were subsequently exposed to the anti-cancer drug Gemcitabine. This way, the researchers were able to identify a new dCK variant, which they named G12, that made tumor cells much more sensitive to the anti-cancer drug (60 times more when compared to cells with the ‘regular’ cDK, and 300 times more when compared to cells without the protein). So, the use of G12 could lead to lowering the required doses of anti-cancer drugs, thereby countering the unwanted and unpleasant side-effects and improving their effectiveness.
Upon investigation of G12, the scientists found that the mutations characterizing the variant were located far away from the active site of the protein and, therefore, would have been completely “unpredictable on a rational basis”.
According to the authors, this new Retrovolution system can be used to generate large libraries of gene and protein variants, which may prove useful in many therapeutic applications, ranging from cancer treatment to transplantation medicine.
Photo credit: Wikimedia Commons, author: CDC/C. Goldsmith, P. Feorino, E.L. Palmer, W.R. McManus.
Rossolillo P, Winter F, Simon-Loriere E, Gallois-Montbrun S, & Negroni M (2012). Retrovolution: HIV-Driven Evolution of Cellular Genes and Improvement of Anticancer Drug Activation. PLoS genetics, 8 (8) PMID: 22927829