p53 actions on microRNA expression and maturation pathway.

The tumor suppressor p53 orchestrates multiple cellular pathways as a central node of anti-oncogenic programs in response to DNA damage, oncogene activation, and several stresses. In addition to the principal role as a transcription factor that transactivates many target genes involved in apoptosis and cell cycle control, p53 has been shown to exert various transactivation-independent effects both in the nucleus and in the cytoplasm. Diversity of p53 activities is further emphasized by the recent studies revealing the close interaction between the p53 and microRNA (miRNA) world. We recently demonstrated that p53 promotes the processing of several primary miRNA transcripts through association with Drosha, a central RNase III in miRNA biogenesis, under DNA damage-inducing conditions. In contrast to wild-type p53, cancer-derived p53 mutants attenuate miRNA maturation. These findings reveal a novel aspect of p53 activities and suggest complex crosstalks between miRNA biogenesis and intracellular signaling pathways. In this chapter, we describe the methods for evaluation of the effects of p53 on miRNA expression, an interaction between pri-miRNA and Drosha complex, and pri-miRNA processing activity of the Drosha complex.