MicroRNAs (miRNAs) are small noncoding RNAs that regulate cognate mRNAs at the post-transcriptional stage. Several studies have shown that miRNAs modulate gene expression in mammalian cells by base pairing to complementary sites in the 3′-untranslated region (3′-UTR) of the target mRNAs. In the present study, miR-24 was found to target fas associated factor 1(FAF1) by binding to its amino acid coding sequence (CDS) region, thereby regulating apoptosis in DU-145 cells. This result supports an augmented model whereby animal miRNAs can exercise their effects through binding to the CDS region of the target mRNA. Transfection of miR-24 antisense oligonucleotide (miR-24-ASO) also induced apoptosis in HGC-27, MGC-803 and HeLa cells. We found that miR-24 regulates apoptosis by targeting FAF1 in cancer cells. These findings suggest that miR-24 could be an effective drug target for treatment of hormone-insensitive prostate cancer or other types of cancers. Future work may further develop miR-24 for therapeutic applications in cancer biology.

As a major component of the cytoskeleton, microtubules consist of αβ-tubulin heterodimers and have been recognized as attractive targets for cancer chemotherapy. Microtubule-stabilizing agents (MSAs) promote polymerization of tubulin and stabilize the polymer, preventing depolymerization. The molecular mechanisms by which MSAs stabilize microtubules remain elusive. Here we report a 2.05 Å crystal structure of tubulin complexed with taccalonolide AJ, a newly identified taxane-site MSA. Taccalonolide AJ covalently binds to β-tubulin D226. On AJ binding, the M-loop undergoes a conformational shift to facilitate tubulin polymerization. In this tubulin–AJ complex, the E-site of tubulin is occupied by GTP rather than GDP. Biochemical analyses confirm that AJ inhibits the hydrolysis of the E-site GTP. Thus, we propose that the β-tubulin E-site is locked into a GTP-preferred status by AJ binding. Our results provide experimental evidence for the connection between MSA binding and tubulin nucleotide state, and will help design new MSAs to overcome taxane resistance.