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: We then determined the mechanisms involved in the decreased stability of CerS1 mRNA in HNSCC cells compared to keratinocytes. It is known that CerS1 has two possible alternatively spliced variants. CerS1-1 is a bi-cistronic mRNA containing both CerS1 and GDF1 (Wang et al, 2007), growth and differentiation factor 1, coding sequences (Fig 6A). CerS1/GDF1 bi-cistronic mRNA is controlled by a common promoter element at the upstream of the 5′-end of the CerS1 gene (exons1–7), and by a 3′UTR poly-adenylation (polyA) sequence (AATAAA), present at the 3′-end of the GDF1 gene. According to mirBase, there are no known miR-target sequences at the 3′UTR of the CerS1/GDF1 bicistronic pre-mRNA (CerS1-1). The alternatively spliced variant of CerS1-2 contains exons 1–6, but not exon 7 and the intronic sequence between exons 6 and 7 contains six putative poly(A)-signals (A1–A6), indicating that this intronic sequence might be utilized as a 3′UTR of the CerS1-2 mRNA (Fig 6A). In fact, analysis of the CerS1-2 3′UTR sequence revealed that there is a hsa-miRNA-574-5p-target sequence upstream of the putative A5–A6 poly-A sequences (Fig 6A and Fig S4A of Supporting Information). This finding suggested that the expression of CerS1-2 mRNA might be regulated by miR-574-5p.
Affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, SC, USA.