The transcriptional profiles and functional implications of long non-coding RNAs in the unfolded protein response.

The unfolded protein response (UPR) is activated, when the folding capacity is compromised in the endoplasmic reticulum (ER). To date, most studies focused on the coding genes and microRNAs in UPR. Other non-coding RNAs affected by UPR and their roles in UPR have not been systematically studied. Long noncoding RNAs (lncRNAs) are increasingly recognized as powerful epigenetic regulators. In this study, we transcriptomically profiled the lncRNAs and mRNAs from mouse embryonic fibroblasts under ER stress, and identified many differentially expressed lncRNAs and mRNAs. Genomic location and mRNA-lncRNA co-expression analyses predicted a number of lncRNAs, which potentially regulate the expression of UPR genes. In particular, FR229754, an exonic sense lncRNA, is significantly up-regulated in UPR. FR229754 overlaps with Sel1l, and their expressions correlated with each other. Sel1l is involved in the ER-associated protein degradation. Silencing of FR229754 did not much affect the expression of Sel1l, but markedly reduced the levels of BiP/GRP78/Hspa5, a major ER chaperon up-regulated in UPR. Probing with pathway-specific inhibitors showed that up-regulation of FR229754 and Sel1 depended on the activation of PERK. Together, our study identified a number of candidate lncRNAs and paved the way for future characterization of their functions in UPR.