Morphological alteration of X-ray induced partially transformed human cells by transfection with a small c-myc DNA sequence

During attempts to transform a normal human fibroblast strain (GM730) by X- irradiation, we obtained a partially transformed cell strain (GM730pt) whic h demonstrates several aspects of the transformed phenotype including morph ological changes, increased saturation density, growth in soft agar, and fo cus formation in long-term cultures. When GM730pt cells were transfected wi th the feline c-myc gene, morphology of the cells changed dramatically foll owing seven days of expression. Transfection of other plasmid DNAs or oncog enes such as pUC8, pSV2neo, src, sis, and H-ras had little or no effects on the phenotype of GM730pt cells. On the other hand, a gel purified, small f ragment of c-myc DNA had a complete cell alteration activity. Furthermore, Bal 31 deletion and M13 sequencing experiments showed that the alteration s een in GM730pt cells is delimited to a 24 nucleotide stretch (active myc el ement) from the second intron of the feline c-myc gene that contains a T-ri ch sequence. (C) 2000 Academic Press.