Concerted functions of HDAC1 and microRNA-574-5p repress alternatively spliced ceramide synthase 1 expression in human cancer cells.
Bottom Line: Moreover, an alternatively spliced variant CerS1 mRNA (CerS1-2) was detected mainly in cancer cells or primary tumour tissues compared to controls, which was targeted by miR-574-5p for degradation.A specific 3'UTR-targeting site, localized within the retained intron between exons 6 and 7, was identified, and its mutation, or miR-574-5p knockdown prevented the degradation of CerS1-2 mRNA.Accordingly, knockdown of CerS1 partially protected cancer cells from MS-275/miR-574-5p siRNA-mediated growth inhibition.
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC, USA.Show MeSH
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Mentions: Moreover, we determined which HDAC was involved in the repression of the CerS1 promoter in HNSCC cells. First, UM-SCC-1 cells were treated with the known HDAC1-specific inhibitor MS-275, a pan class I-HDAC inhibitor BML-210 or a class II-HDAC inhibitor dPAHA (Yang & Seto, 2008), and then their effects on CerS1 promoter activity were examined. Whereas, the class II-HDAC inhibitor dPAHA had no significant effect, inhibition of class-I HDACs using BML-210 or HDAC1 using MS-275 enhanced the CerS1 promoter by about 3- or 4-fold, respectively (Fig 5A). Accordingly, MS-275 treatment increased Sp1 recruitment to the CerS1 promoter DNA compared to controls (Fig 5B), as determined by Q-ChIP. Thus, these data suggest that a class I HDAC, possibly HDAC1 might be involved in the repression of the CerS1 promoter in HNSCC cells. Indeed, knockdown of HDAC1, but not other class-I HDACs (HDAC2, HDAC3 or HDAC8) using siRNAs (decreasing their target gene mRNA expression by about 50–90%, as determined by Q-PCR, Fig S3A of Supporting Information) increased the activity of the CerS1 core promoter (Fig 5C). Thus, these data suggest that the CerS1 promoter is repressed mainly by an HDAC1-dependent mechanism, and that inhibition of HDAC1 using MS-275 or HDAC1-siRNAs activates the CerS1 promoter.
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC, USA.