Figure 1. IR induces miR-34a expression in rat mammary gland and HMEC cells in a dose- and time-dependent manner. (A) Total RNA isolated from mammary gland tissue of 6-wk-old female Long-Evans rats exposed to either 30 kVp/0.1 Gy or 80 kVp/2.5 Gy X-ray or left sham-treated as controls 96 h post-irradiation was subjected to microRNA microarray, as described in “Materials and Methods.” (B and C) Total RNA was isolated from mammary gland tissue of 6-wk-old female Long-Evans rats, as described in (A), and the levels of rno-miR-34a were examined by real-time RT-PCR, as described in “Materials and Methods.” (D) Total RNA was isolated from HMEC cells exposed to either 30 kVp/0.1 Gy or 80 kVp/2.5 Gy X-ray or left unexposed as control 96 h post-irradiation; the level of hsa-miR-34a was determined by real-time RT-PCR, as described in “Material and Methods.” (E and F) Genomic DNAs were extracted from IR-exposed HMEC cells; miR-34a gene copy number and promoter CpG island methylation were determined, as described in “Materials and Methods.” The asterisk indicates p < 0.05.