VARIABLE ABERRANT CDNAS IN SINGLE DIPHTHERIA TOXIN-RESISTANT HUMAN FIBROBLASTS

We treated transformed human fibroblasts with diphtheria toxin (DT) an d isolated 40 single cells that were toxin resistant but unable to pro pagate. In 13 of them toxin resistance was associated with the presenc e of one or more aberrant transcripts of the structural gene for elong ation factor 2 (EF-2). cDNA obtained from these transcripts had 164-44 7 bp-long deletions. Each of these deletions was associated with 2-8 b ase pairs-long repeats at its breakpoints. Only 10 out of 16 cDNA dele tions were associated with presumed exon junctions. A role is suggeste d for errors in transcription in producing the aberrant transcripts wh ich gave rise to the deletion-bearing cDNA species. (C) 1997 Elsevier Science B.V.