PURPOSE: To determine the sequence of DNA and the sequence of amino acids estimated therefrom by cloning the cDNA of a peroxisome-forming factor from a mammalian cell with the utilization of genetic complementarity.

CONSTITUTION: Cells (CHO) originated from the ovarium of a Chinese hamster is subjected to a variation treatment, and a variant cell (the formation of the peroxisome is not recognized morphologically and the biochemical properties are highly similar to those of fibroblasts originated from a patient of Zwellweger syndrome), lacking a peroxisome type dihydroxyacetone phosphate acyltransferase, is separated from the treated cells. The separated variant cell is subjected to a transfection with a cDNA library originated from rat liver and a cell (having a peroxisome-forming ability) whose variation is genetically complemented is selected. The selected cell is fused with a COS cell and cDNA is recovered. The cDNA of a peroxisome-forming factor is isolated from the clone.