YAC Transfer into Mammalian Cells by Cell Fusion

The large regions of DNA that can be cloned in yeast artificial chromosomes (YACs) are ideal for expression studies of the complex genes and gene clusters found in the mammalian genome. Such studies require that the YAC of interest be transferred into a suitable expression system, such as mammalian cells in tissue culture or transgenic animals. Recent experiments indicate that large genes cloned on YACs may be transferred intact and are often expressed at a level comparable to the endogenous genes and in a fully controlled fashion owing to the large amount of flanking DNA containing long range controlling elements (reviewed in ref. 1 ).