The present studies have examined the effects of ionizing radiation on control of the early growth response 1 (EGR1) gene. Exposure of human HL-525 cells to x-rays was associated with increases in EGR1 mRNA levels. Nuclear run-on assays showed that this effect is related at least in part to activation of EGR1 gene transcription. Sequences responsive to ionizing radiation-induced signals were determined by deletion analysis of the EGR1 promoter. The results demonstrate that x-ray inducibility of the EGR1 gene is conferred by a region containing six serum response or CC(A+T-rich)6GG (CArG) motifs. Further analysis confirmed that the region encompassing the three distal or upstream CArG elements is functional in the x-ray response. Moreover, this region conferred x-ray inducibility to a minimal thymidine kinase gene promoter. Taken together, these results indicate that ionizing radiation induces EGR1 transcription through CArG elements.

Original languageEnglish
Pages (from-to)10149-10153
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number21
StatePublished - 1992


  • Early growth response
  • Serum response element
  • X-rays


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