Hypoxia plays a crucial role in the aggressiveness of solid tumors by driving multiple signaling pathways. Recently, long non-coding RNA (lncRNA) has been reported to promote or inhibit tumor aggressiveness by regulating gene expression. Previous studies in our laboratory found that the lncRNA NDRG1-OT1 is significantly up-regulated under hypoxia and inhibits its target gene NDRG1 at both the mRNA and protein levels. At the protein level, NDRG1-OT1 increases NDRG1 degradation via ubiquitin-mediated proteolysis. However, the repressive mechanism of NDRG1 at the RNA level is still unknown. Therefore, the purpose of this study was to study how NDRG1-OT1 transcriptionally regulates its target gene NDRG1. Luciferase reporter assays showed that NDRG1-OT1 decreased NDRG1 promoter activities. Mass spectrometry, bioinformatics tools, genetic manipulation, and immunoblotting were used to identify the interacting proteins. Surprisingly, different fragments of NDRG1-OT1 had opposite effects on NDRG1. The first quarter fragment (1–149 nt) of NDRG1-OT1 had no effect on the NDRG1 promoter; the second quarter fragment (150–263 nt) repressed NDRG1 by increasing the binding affinity of HNRNPA1; the third quarter fragment (264–392 nt) improved NDRG1 promoter activity by recruiting HIF-1α; the fourth quarter fragment (393–508 nt) down-regulated NDRG1 promoter activity via down-regulation of KHSRP under hypoxia. In summary, we have found a novel mechanism by which different fragments of the same lncRNA can cause opposite effects within the same target gene.
CITATION STYLE
Yeh, C. C., Luo, J. L., Nhut Phan, N., Cheng, Y. C., Chow, L. P., Tsai, M. H., … Lai, L. C. (2018). Different effects of long noncoding RNA NDRG1-OT1 fragments on NDRG1 transcription in breast cancer cells under hypoxia. RNA Biology, 15(12), 1487–1498. https://doi.org/10.1080/15476286.2018.1553480
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