Exploration of Alternative Mechanism for MiR-596-mediated Down-regulation of LGALS3BP in Oral Squamous Cell Carcinoma.

MicroRNAs (miRNAs) are endogenous small non-coding RNAs that negatively regulate gene expression via binding to the 3' -untranslated region (UTR) of transcripts. However, recent evidence suggests that miRNA can also bind to the open reading frame (ORF) region within transcripts for its down-regulation. On the other hand, a previous report demonstrated that miR-596 has a tumor suppressor function by targeting LGALS3BP via directly binding to its 3' UTR in oral squamous cell carcinoma (OSCC) cells. However, it is not clear whether this miRNA can bind to the ORF region of LGALS3BP. In this study, although four putative binding sites of miR-596 were included within the ORF region of LGALS3BP, it was found that miR-596 could not bind to those sites. Instead, the results showed that the expression of LGALS3BP might be in part negatively regulated by the proteasome system at the protein level. Thus, these findings may help clarify the molecular mechanism of the tumor-suppressive effect through down-regulation of LGALS3BP by miR-596 in OSCC cells.