Steroidal regulation of uterine miRNAs is associated with modulation of the miRNA biogenesis components Exportin-5 and Dicer1.

MicroRNAs (miRNAs) are small, non-coding RNA molecules which post-transcriptionally regulate gene expression. We have previously demonstrated that within the uterus, miRNA expression is under steroidal control and that disruption of Dicer1, the enzyme which generates mature miRNAs, leads to abnormalities in the development and function of the female reproductive tract. Despite the apparent importance of miRNAs and the enzymes which lead to their generation, little to no information exists on the mechanisms which regulate the expression of this system in the female reproductive tract. The objective of the current study was to examine steroidal regulation of the miRNAs biogenesis enzymes, Drosha, Dgcr8, Exportin-5 and Dicer1 in the mouse uterus. The results of this study indicate that estrogen and progesterone significantly increased Exportin-5 mRNA expression while only progesterone increased Dicer1 expression. We conclude from these studies that the miRNA biogenesis components Drosha, Dgcr8, Exportin-5 and Dicer1 are expressed in the mouse uterus and that Exportin-5 and Dicer1 appear to be the major steroid regulated components in the miRNA biogenesis pathway. These observations suggest that in addition to steroids modulating miRNA expression at the level of transcription, they may also influence miRNA expression by regulating the expression of the miRNA biogenesis components necessary for their processing to the mature cytoplasmic form.