About 8 kb of sequence spanning 3' of intron 1 through exon 4 was replaced with the human LDLR minigene containing exons 2-18 of human sequence. The minigene was shortened by a deletion of two of the three 3' AU-rich elements in exon 18. The mature protein transcribed from the chimeric gene was entirely human protein, due to exon 1 encoding only the signal peptide. (J:67282)