Expression of DNA transferred into mammalian cells

Abstract

There are several methods to introduce purified DNA into mammalian cells. These include microinjection into the nuclei of the recipient cells and complexing the DNA with facilitating agents such as calcium-phosphate. After it enters the nucleus, the DNA is expressed in a large proportion of the cells. This expression is dependent upon cis-acting sequences that are recognized by the mammalian transcriptional and translational machinery. In a smaller proportion of cells, the exogenous DNA becomes covalently integrated into the host cell DNA at random sites. Non-selectable genes can be introduced into mammalian cells by ligating them to a selectable marker or mixing the DNA with carrier DNA containing a selectable marker. The DNA that is introduced into mammalian cells can be rescued for examination and analysis. These gene transfer methods have already proven to be useful in identification of sequences which are necessary for normal gene expression as well as gene regulation. In addition a number of genes have been isolated using gene transfer methods. DNA mediated gene transfer holds much promise to target genes to specific sites in the chromosomes, to understand mechanisms of mammalian development and cell differentiation and is expected to provide a method to produce important and novel gene products that may be used for diagnostic and therapeutic purposes.