MicroRNAs: new players in the DNA damage response.

The DNA damage response (DDR) is a signal transduction pathway that decides the cell's fate either to repair DNA damage or to undergo apoptosis if there is too much damage. Post-translational modifications modulate the assembly and activity of protein complexes during the DDR pathways. MicroRNAs (miRNAs) are emerging as a class of endogenous gene modulators that control protein levels, thereby adding a new layer of regulation to the DDR. In this review, we describe a new role for miRNAs in regulating the cellular response to DNA damage with a focus on DNA double-strand break damage. We also discuss the implications of miRNA's role in the DDR to stem cells, including embryonic stem cells and cancer stem cells, stressing the potential applications for miRNAs to be used as sensitizers for cancer radiotherapy and chemotherapy.