Bcr‐Abl regulation of sphingomyelin synthase 1 reveals a novel oncogenic‐driven mechanism of protein up‐regulation

Abstract

Bcr-Abl (break-point cluster region-abelson), the oncogenic trigger of chronic myelogenous leukemia (CML), has previously been shown to up-regulate the expression and activity of sphingomyelin synthase 1 (SMS1), which contributes to the proliferation of CML cells; however, the mechanism by which this increased expression of SMS1 is mediated remains unknown. In the current study, we show that Bcr-Abl enhances the expression of SMS1 via a 30-fold up-regulation of its transcription. Of most interest, the Bcr-Abl-regulated transcription of SMS1 is initiated from a novel transcription start site (TSS) that is just upstream of the open reading frame. This shift in TSS utilization generates an SMS1 mRNA with a substantially shorter 5' UTR compared with its canonical mRNA. This shorter 5' UTR imparts a 20-fold greater translational efficiency to SMS1 mRNA, which further contributes to the increase of its expression in CML cells. Therefore, our study demonstrates that Bcr-Abl increases SMS1 protein levels via 2 concerted mechanisms: up-regulation of transcription and enhanced translation as a result of the shift in TSS utilization. Remarkably, this is the first time that an oncogene-Bcr-Abl-has been demonstrated to drive such a mechanism that up-regulates the expression of a functionally important target gene, SMS1.-Moorthi, S., Burns, T. A., Yu, G.-Q., Luberto, C. Bcr-Abl regulation of sphingomyelin synthase 1 reveals a novel oncogenic-driven mechanism of protein up-regulation.

Ceramide/Sphingomyelin Rheostat Regulated by Sphingomyelin Synthases and Chronic Diseases in Murine Models

“…It has also been reported that SMS1 was one of the downstream targets of BCR-ABL signaling. 88 BCR-ABL induces SMS1 transcription from an alternative transcription start site (TSS), leading to increased levels of SMS1 protein and SMS1-mediated proliferation. Indeed, BCR-ABL-positive K562 cells showed 70-fold up-regulation of SMS1 transcription as compared with BCR-ABL-negative HL-60 cells.…”

Sphingomyelin Synthase 1 (SMS1) Downregulation Is Associated With Sphingolipid Reprogramming and a Worse Prognosis in Melanoma

“…Moreover, 4 deep deletions were identified as well as 17 CpG located on the two CpG islands and their shores, the methylation of which was correlated with SGMS1 downregulation in metastatic melanoma. SMS1 expression and activity are likely regulated by translational and post-translational mechanisms such as recently described in Bcr-Abl-expressing leukemia cells (Moorthi et al, 2018). Whereas key driver mutations have been identified in melanoma (Hodis et al, 2012), we found no correlation between mutation status and SL signature.…”

Regulation of human sphingomyelin synthase 1 translation through its 5′‐untranslated region

“…All constructs and their characteristics are listed in Tables 1 and 2. GFP transcripts carrying SGMS1 5 0 UTR IIb (IIb-GFP) or 7 (7-GFP) [28] were synthesized by GenScript USA Inc. (Piscataway, NJ, USA) and cloned into the pUC57 plasmid flanked by sequences for the restriction enzymes BamH1 (at 5 0 ) and Xba1 (at 3 0 ). The GFP sequence from Aequorea Victoria (Av, Jellyfish, Takara Bio, Mountain View, CA, USA, formerly Clontech) was utilized.…”

“…All SGMS1 deletion/mutation constructs were obtained by PCR using the Phusion High-fidelity DNA polymerase (NEB Inc. Ipswich, MA, USA) according to manufacturer's instructions and, as template, the previously characterized wild-type transcript IIb-SGMS1 [28]. A list of all primers' combinations can be found in Table 3 while the sequences for IIb-SGMS1 and 7-SGMS1 can be found in Table 4.…”

“…Using a cell model for chronic myelogenous leukemia (CML), it was shown that the Bcr-abl 1 oncogene, etiological agent for CML, promoted SGMS1 expression and activity which in turn sustained proliferation of Bcr-abl 1-positive leukemic cells [27]. A recent follow-up study demonstrated that the regulation of SMS1 in CML was driven by a novel mechanism of oncogenic-mediated protein upregulation promoted by the presence of Bcr-abl 1 [28]. Bcr-Abl 1 caused an increase in SGMS1 transcription from a novel start site (TSS-7) which resulted in an SGMS1 transcript with a significantly shorter 5 0 -UTR (7-SGMS1).…”