miR-128 Is Implicated in Stress Responses by Targeting MAFG in Skeletal Muscle Cells

Abstract EN

MAFG (v-Maf avian musculoaponeurotic fibrosarcoma oncogene homolog G) is a bZIP-type transcriptional regulator that belongs to the small MAF (sMAFs) protein family.

By interacting with other bZIP transcription factors, sMAFs can form homo- and heterodimers governing either repressive or activating transcriptional functions.

As heterodimeric partner of Nrf2, MAFG positively influences the ARE-dependent antioxidant/xenobiotic pathways, at least in condition of a correct MAFG:Nrf2 balance.

MicroRNAs (miRs) participate to different regulatory networks being involved as fine-tuning regulators of gene expression.

However, the connections between cellular surveillance to stresses mediated by MAFG:Nrf2 and miR regulations are not well understood.

Here, we explored the impact of miR-128 in expression of genes related to stress response.

Bioinformatic predictions coupled with functional analysis revealed the presence of miR-128 binding site in the 3′UTR of MAFG.

Ectopic miR-128 expression correlated with reduced expression of endogenous MAFG-dependent genes and negatively affected ARE-mediated molecular phenotype based on Nrf2 activity.

Indeed, miR-128 impairs redox-dependent pathways induced in response to oxidative stress.

Moreover, in condition of hypoxia, MAFG induction correlated with reduced levels of miR-128.

This lead to increased mRNA levels of HMOX-1 and x-CT for blunting stress.

Overall, these findings identify MAFG as novel direct target of miR-128.