Expression of versican 3'-untranslated region modulates endogenous microrna functions

Abstract

Background: Mature microRNAs (miRNAs) are single-stranded RNAs that regulate post-transcriptional gene expression. In our previous study, we have shown that versican 39UTR, a fragment of non-coding transcript, has the ability to antagonize miR-199a-3p function thereby regulating expression of the matrix proteins versican and fibronectin, and thus resulting in enhanced cell-cell adhesion and organ adhesion. However, the impact of this non-coding fragment on tumorigenesis is yet to be determined. Methods and Findings: Using computational prediction confirmed with in vitro and in vivo experiments, we report that the expression of versican 39UTR not only antagonizes miR-199a-3p but can also lower its steady state expression. We found that expression of versican 39UTR in a mouse breast carcinoma cell line, 4T1, decreased miR-199a-3p levels. The decrease in miRNA activity consequently translated into differences in tumor growth. Computational analysis indicated that both miR- 199a-3p and miR-144 targeted a cell cycle regulator, Rb1. In addition, miR-144 and miR-136, which have also been shown to interact with versican 39UTR, was found to target PTEN. Expression of Rb1 and PTEN were up-regulated synergistically in vitro and in vivo, suggesting that the 39UTR binds and modulates miRNA activities, freeing Rb1 and PTEN mRNAs for translation. In tumor formation assays, cells transfected with the 39UTR formed smaller tumors compared with cells transfected with a control vector. Conclusion: Our results demonstrated that a 39UTR fragment can be used to modulate miRNA functions. Our study also suggests that miRNAs in the cancer cells are more susceptible to degradation, due to its interaction with a non-coding 39UTR. This non-coding component of mRNA may be used retrospectively to modulate miRNA activities. © 2010 Lee et al.