ALTERATIONS IN TRANSCRIPTION FACTOR-BINDING IN RADIORESISTANT HUMAN-MELANOMA CELLS AFTER IONIZING-RADIATION

We analyzed alterations in transcription factor binding to specific, k nown promoter DNA consensus sequences between irradiated and unirradia ted radioresistant human melanoma (U1-Mel) cells. The goal of this stu dy was to begin to investigate which transcription factors and DNA-bin ding sites are responsible for the induction of specific transcripts a nd proteins after ionizing radiation (Boothman et al., Proc. Natl. Aca d. Sci. USA 90, 7200, 1993). Transcription factor binding was observed using DNA band-shift assays and oligonucleotide competition analyses. Confluence-arrested U1-Mel cells were irradiated (4.5 Gy) and harvest ed at 4 h. Double-stranded oligonucleotides containing known DNA-bindi ng consensus sites for specific transcription factors were used. Incre ased DNA-binding activity after ionizing radiation was noted with olig onucleotides containing the CREB, NF-kappa B and Sp1 consensus sites. Increased DNA binding activity after ionizing radiation was noted with oligonucleotides containing the CREB, NF-kappa B and Sp1 consensus si tes. No changes in protein binding to AP-1, AP-2, AP-3, or CTF/NF1, GR E or Oct-1 consensus sequences were noted. X-ray activation of select transcription factors, which bind certain consensus sites in promoters , may cause specific induction or repression of gene transcription.