RNA interference & inhibition of viruses.

147 RNA interference (RNAi) is emerging as a new strategy to selectively shut off the post-transcriptional expression of mRNA. This evolutionarily maintained mechanism has been detected from yeast to mammalian cells. Rapid, inexpensive and selective silencing of a gene product in complex biological systems obviously has opened new avenues in fields of virology, cancer research, genetic disorders, drugs designing, etc. Temperature-sensitive (ts) mutants have been extensively used in virus research prior to development of polymerase chain reaction (PCR), nucleotide sequencing and other molecular methods. These mutants were either spontaneous or chemically induced. Single point mutation would render the gene product completely or partially nonfunctional at elevated temperatures. Such single point mutants with ts marker proved to be extremely useful in understanding genetic complementation/ recombination, identification of involvement of specific gene(s) in early or late stage of virus replication, RNA or DNA synthesis, etc . Subsequently, the technology of specifically knocking out genes in whole animals became available to study the role of a particular gene in a cascade of events and its effect on phenotypic expression. The RNAi technology scores over such approaches with its ease, cost-effectiveness and rapidity.