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Aberrant splicing of cdkn1a/p21 through micro-RNA mediated downregulation of JMJD6

ABSTRACT: Post-transcriptional modifications of tumor suppressors, including microRNA-mediated downregulation, are important events in tumor progression. To identify microRNAs involved in oncogenic transformation, we examined global microRNA profiles of three ras transgenic zebrafish models. Four microRNAs are upregulated in all transgenic systems. Analysis of the predicted targets shows that three of them target Jmjd6, and overexpression of Jmjd6 in ras transformed melanocytes blocks proliferation and melanoma development. We found that Jmjd6 functions to regulate splicing of the tumor suppressor cdkn1a/p21. Truncated cdkn1a/p21 transcripts, lacking the PCNA binding domain, accumulate in ras-expressing melanocytes during melanoma development. These findings implicate Jmjd6 in a novel mechanism for inactivation of a major tumor suppressor pathway in melanoma.

ORGANISM(S): Danio rerio

PROVIDER: GSE37015 | GEO | 2017/01/01

SECONDARY ACCESSION(S): PRJNA157497

REPOSITORIES: GEO

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Project description:Melanocytes within benign human nevi are the paradigm for tumor suppressive senescent cells in a pre-malignant neoplasm. These cells typically contain mutations in either the BRAF or N-RAS oncogene and express markers of senescence, including p16. However, a nevus can contain 10s to 100s of thousands of clonal melanocytes and approximately 20-30% of melanoma are thought to arise in association with a pre-existing nevus. Neither observation is indicative of fail-safe senescence-associated proliferation arrest and tumor suppression. We set out to better understand the status of nevus melanocytes. Proliferation-promoting Wnt target genes, such as cyclin D1 and c-myc, were repressed in oncogene-induced senescent melanocytes in vitro, and repression of Wnt signaling in these cells induced a senescent-like state. In contrast, cyclin D1 and c-myc were expressed in many melanocytes of human benign nevi. Specifically, activated Wnt signalling in nevi correlated inversely with nevus maturation, an established dermatopathological correlate of clinical benignancy. Single cell analyses of lone epidermal melanocytes and nevus melanocytes showed that expression of proliferation-promoting Wnt targets correlates with prior proliferative expansion of p16-expressing nevus melanocytes. In a mouse model, activation of Wnt signaling delayed, but did not bypass, senescence of oncogene-expressing melanocytes, leading to massive accumulation of proliferation-arrested, p16-positive non-malignant melanocytes. We conclude that clonal hyperproliferation of oncogene-expressing melanocytes to form a nevus is facilitated by transient delay of senescence due to activated Wnt signaling. The observation that activation of Wnt signaling correlates inversely with nevus maturation, an indicator of clinical benignancy, supports the notion that persistent destabilization of senescence by Wnt signaling contributes to the malignant potential of nevi. We used RNA-Seq to detail the global programme of gene expression in human melanoma cell lines

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Aberrant splicing of cdkn1a/p21 through micro-RNA mediated downregulation of JMJD6

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