The online version of this article (doi:10.1186/s13046-017-0521-5) contains supplementary material, which is available to authorized users.
RNA-binding protein 38 (RBM38) is a member of the RNA recognition motif (RRM) family of RNA-binding proteins (RBPs). RBM38 often exerts its function by forming regulatory loops with relevant genes. c-Myc is an oncogenic transcription factor that is upregulated in one-third of breast cancers and involved in many cellular processes in this malignancy. In our previous study, RBM38 was identified as a tumor suppressor in breast cancer. In the present study, we investigated the mechanisms underlying the regulation of this tumor suppressor.
Lentivirus transfections, Western blotting analysis, qRT-PCR and immunohistochemistry were employed to study the expression of c-Myc and RBM38. Chromatin immunoprecipitation and dual-luciferase reporter assays were performed to investigate the direct relationship between c-Myc protein and the RBM38 gene. RNA immunoprecipitation combined with dual-luciferase reporter assays was conducted to confirm the direct relationship between the RBM38 protein and the c-Myc transcript.
Knockdown of c-Myc increased RBM38 expression by binding directly to specific DNA sequences (5′-CACGTG-3′), known as the E-box motif, in the promoter region of RBM38 gene. Additionally, RBM38 destabilized the c-Myc transcript by directly targeting AU-rich elements (AREs) in the 3′-untranslated region (3′-UTR) of c-Myc mRNA to suppress c-Myc expression. Moreover, specific inhibitors of c-Myc transcriptional activity inhibited RBM38-induced suppression of growth, implying that RBM38 acts as a tumor suppressor via a mechanism that depends, at least partially, on the reduction of c-Myc expression in breast cancer.
RBM38 and c-Myc form a unique mutually antagonistic RBM38-c-Myc loop in breast cancer.
Additional file 1: Table S1. Sequence of REMSA probes. Table S2. The primers used in quantitative RT-PCR. (DOC 38 kb)13046_2017_521_MOESM1_ESM.doc
Additional file 2: Figure S1. RBM38 and c-Myc cellular localization in breast cancer cells with immunofluorescence. IF staining of RBM38 in MCF-7 and ZR-75-1 cells at 400× magnification. Green represented c-Myc staining, Red represented RBM38 staining. Blue represented nuclear DNA staining with DAPI. Scale bars indicate 20 μm. (a, b) RBM38 and c-Myc were expressed in the cytoplasm and nucleus in breast cancer cells. (JPG 3735 kb)13046_2017_521_MOESM2_ESM.jpg
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- The role of c-Myc-RBM38 loop in the growth suppression in breast cancer
- BioMed Central
Journal of Experimental & Clinical Cancer Research
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