Isolation of x-ray-inducible transcripts from radioresistant human melanoma cells

David A. Boothman, Mark Meyers, Nina Fukunaga, Sam W. Lee

Research output: Contribution to journalArticlepeer-review

132 Scopus citations


Twelve x-ray-induced transcripts (xips), differentially expressed 8- to 230-fold in x-irradiated versus unirradiated radioresistant human melanoma (U1-Mel) cells, were isolated as cDNA clones (xip1 through xip12) after four rounds of differential hybridization. Northern analyses revealed rare, medium, and abundant xips, ranging in size from 1.2 to 10 kb. All transcripts were transiently expressed and induced by low, but not by high (>600 cGy), doses of radiation. Three transcripts (xip4, -7, and -12) were induced only by ionizing radiation, and many (i.e., xip1, -2, -3, -5, -6, -8, -9, -10, and -11) were also induced by UV irradiation or phorbol 12-myristate 13-acetate. Heat shock did not induce any of the xips, but it decreased basal levels of xip4, -7, -11, and -12. Three xip cDNA clones were identified as encoding thymidine kinase, DT diaphorase, and tissue-type plasminogen activator. The remaining nine cDNA clones showed little homology to known genes. Three clones contained regions homologous to c-fes/fps protooncogene, recombination activating gene 1, or the human angiogenesis factor gene. X-ray-inducible genes may function in damaged cells to regulate DNA repair, apoptosis, mutagenesis, and carcinogenesis.

Original languageEnglish (US)
Pages (from-to)7200-7204
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number15
StatePublished - 1993


  • cDNA cloning
  • differential hybridization
  • gene expression
  • ionizing radiation

ASJC Scopus subject areas

  • General


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