The introduction of recombinant DNA has become a common tool for studying functional and structural properties of a wide variety of proteins. Functional analysis of protein can be studied by suppression of gene expression, thus introducing a plasmid which expresses an antisense RNA in mammalian cells. Several extracellular matrix proteins require an assembly of subunits to form functional heteromultimers with distinct features. Thus, expression of a specific mutant protein can interfere with the assembly of multimeric protein, resulting in a dominant-negative phenotype. In these studies, an efficient delivery of DNA into appropriate target cells represents a critical step. Although many procedures of transfection of the plasmid DNA into mammalian cells are available, viral infection represents a far superior mode of delivery because retroviral vectors were shown to transduce genes of interest into tissue-culture cells with success rates approaching 100%. The retrovirus inserts the viral genome into the chromosome of the infected cell permanently, usually without any measurable effect on the viability of the infected cells. The result is an efficient gene-transfer system in which most recipient cells will incorporate and express the transduced gene.
