NEW VECTOR FOR TRANSFER OF YEAST ARTIFICIAL CHROMOSOMES TO MAMMALIAN-CELLS

A modification vector has been constructed to facilitate the transfer of yeast artificial chromosomes (YACs) to mammalian cells in culture b y targeting a dominant selectable marker (G418 resistance) to the righ t arm of pYAC4 clones. The ADE2 gene is used for yeast selection with consequent disruption of the URA3 gene, allowing direct modification o f YACs within the common host strain AB1380, and providing a simple te st for correct targeting. This vector has been tested by modification of a 550-kb YAC containing part of the human MHC class II region and t ransfer to CHO cells by protoplast fusion. Analysis of 15 independent G418-resistant CHO lines obtained following fusion suggests the majori ty contain a complete YAC with moderate amplification in some lines.