MicroRNA-340-mediated Degradation of Microphthalmia-associated Transcription Factor (MITF) mRNA Is Inhibited by Coding Region Determinant-binding Protein (CRD-BP)

Srikanta Goswami,Rohinton S Tarapore,Ashley M Poenitzsch Strong,Jessica J Teslaa,Yevgenya Grinblat,Vijayasaradhi Setaluri,Vladimir S Spiegelman

doi:10.1074/jbc.m114.590158

Abstract

Alternative cleavage and polyadenylation generates multiple transcript variants producing mRNA isoforms with different length 3'-UTRs. Alternative cleavage and polyadenylation enables differential post-transcriptional regulation via the availability of different cis-acting elements in 3'-UTRs. Microphthalmia-associated transcription factor (MITF) is a master regulator of melanocyte development and melanogenesis. This central transcription factor is also implicated in melanoma development. Here, we show that melanoma cells favor the expression of MITF mRNA with a shorter 3'-UTR. We also establish that this isoform is regulated by a micro RNA (miRNA/miR), miR-340. miR-340 interacts with two of its target sites on the MITF 3'-UTR, causing mRNA degradation as well as decreased expression and activity of MITF. Conversely, the RNA-binding protein, coding region determinant-binding protein, was shown to be highly expressed in melanoma, directly binds to the 3'-UTR of MITF mRNA, and prevents the binding of miR-340 to its target sites, resulting in the stabilization of MITF transcripts, elevated expression, and transcriptional activity of MITF. This regulatory interplay between RNA-binding protein and miRNA highlights an important mechanism for the regulation of MITF in melanocytes and malignant melanomas.

Highlights

Microphthalmia-associated transcription factor (MITF) is paramount for melanocyte development and melanoma pathogenesis
Melanoma Cell Lines Preferentially Express MITF mRNA with a Short 3Ј-UTR—As discussed earlier, several full-length cDNA isoforms of MITF-M with the same coding sequence exist, but the isoforms vary in their 3Ј-UTR length
The finding of one mRNA with different 3Ј-UTRs being regulated by different miRNAs led us to investigate the abundance of the various MITF mRNA isoforms in several melanoma cell lines

Summary

Background

MITF is paramount for melanocyte development and melanoma pathogenesis. Results: CRD-BP restricts the action of miR-340 by preventing its access to the mRNA of MITF, thereby establishing a novel mode for the regulation of MITF. The RNA-binding protein, coding region determinant-binding protein, was shown to be highly expressed in melanoma, directly binds to the 3؅-UTR of MITF mRNA, and prevents the binding of miR-340 to its target sites, resulting in the stabilization of MITF transcripts, elevated expression, and transcriptional activity of MITF. This regulatory interplay between RNA-binding protein and miRNA highlights an important mechanism for the regulation of MITF in melanocytes and malignant melanomas. CRD-BP Prevents miR-340-mediated Degradation of MITF mRNA apart from transcriptional and post-translational regulation, another important mode of regulating gene expression is to manipulate the stability of mature mRNA. Our results here show that CRD-BP restricts the action of miR-340 by preventing its access to MITF mRNA, thereby proposing a novel mode of regulation for MITF

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION