Increased expression of miR-34a in mouse spleen one day after exposure to N-ethyl-N-nitrosourea

MicroRNAs (miRNAs) are a class of single-stranded small RNA molecules (~22 nucleotides) that are not translated into proteins and function as regulators of gene expression. Many miRNAs are involved in carcinogenesis. One of them, miR-34a, is associated with various p53-initiated biological processes and may act as a tumor suppressor miRNA. Its expression is generally down-regulated in tumor tissues and up-regulated in tissues exposed to carcinogens chronically or subchronically. However, the response of this miRNA to acute exposure of a genotoxic carcinogen is little known. In this study, miR-34a expression was evaluated in spleen tissues of mice treated with a dose of 120 mg kg(-1) body weight N-ethyl-N-nitrosourea (ENU), a potent mutagenic carcinogen. Real-time PCR analysis showed that the ENU exposure resulted in a 5.5-fold increase of miR-34a expression over the control one day after the treatment. The result suggests that miR-34a expression responds sensitively to genotoxic insults within a short period after exposure of the mutagen, and therefore, this gene has the potential to be used as an indicator for genotoxin exposure.