MINI-REVIEW miR-421, miR-155 and miR-650: Emerging Trends of Regulation of Cancer and Apoptosis

MicroRNAs have emerged as multifunctional regulators of wide ranging cellular activities. miRNAs are further categorized into tumor suppressor, cancer promoting (oncomirs) and metastasis promoting (metastamirs). miRNA biology is a well orchestrated mechanism that occurs both in nucleus and cytoplasm. RNA polymerase II or III mediate transcription of pri-miRNA. It is cleaved in the nucleus by the microprocessor complex (consisting of the RNase III endonuclease Drosha and the co-factor DGCR8. Recently it has been reported that knockdown of DGCR8 in primary fibroblasts induced senescent phenotype (Gómez-Cabello et al., 2013). Yet another contemporary study revealed that targeted inhibition of DGCR8 remarkably reduced migratory and invasive potential of ovarian cancer cells (Guo et al., 2013). There is another exciting piece of information highlighting role of post-translational modifications for protein stability of Drosha. Drosha is degraded via ubiquitination however if the residues are acetylated, Drosha escapes from degradation. It has been experimentally verified that Deacetylase inhibitors treated cells displayed a rapidly accumulating level of Drosha protein (Tang et al., 2013). In line with similar mechanism, ERK/MAPK mediated phosphorylation of DGCR8 increased its stability (Herbert et al., 2013). The product formed as a result of processing by Drosha-DGCR8 is a precursor hairpin