The melanocortin-1 receptor (MC1R), a G protein-coupled receptor, plays a crucial role in human and mouse pigmentation1–8. Activation of MC1R in melanocytes by α-melanocyte-stimulating hormone (α-MSH)9 stimulates cAMP signaling and melanin production and enhances DNA repair after UV irradiation (UVR)10–16. Individuals carrying MC1R variants, especially those associated with red hair color, fair skin and poor tanning ability (RHC-variants), are associated with higher risk of melanoma5,17,18,19,20. However, how MC1R activity might be modulated by UV irradiation, why redheads are more prone to developing melanoma, and whether the activity of RHC variants might be restored for therapeutic benefit remain unresolved questions. Here we demonstrate a potential MC1R-targeted intervention strategy to rescue loss-of-function MC1R in MC1R RHC-variants for therapeutic benefit based on activating MC1R protein palmitoylation. Specifically, MC1R palmitoylation, primarily mediated by the protein-acyl transferase (PAT) ZDHHC13, is essential for activating MC1R signaling that triggers increased pigmentation, UVB-induced G1-like cell cycle arrest and control of senescence and melanomagenesis in vitro and in vivo. Using C57BL/6J-MC1Re/eJ mice expressing MC1R RHC-variants we show that pharmacological activation of palmitoylation rescues the defects of MC1R RHC-variants and prevents melanomagenesis. The results highlight a central role for MC1R palmitoylation in pigmentation and protection against melanoma.

The major genetic determinants of cutaneous melanoma risk in the general population are disruptive variants (R alleles) in the melanocortin 1 receptor (MC1R) gene. These alleles are also linked to red hair, freckling, and sun sensitivity, all of which are known melanoma phenotypic risk factors. Here we report that in melanomas and for somatic C>T mutations, a signature linked to sun exposure, the expected single-nucleotide variant count associated with the presence of an R allele is estimated to be 42% (95% CI, 15–76%) higher than that among persons without an R allele. This figure is comparable to the expected mutational burden associated with an additional 21 years of age. We also find significant and similar enrichment of non-C>T mutation classes supporting a role for additional mutagenic processes in melanoma development in individuals carrying R alleles.

Highlights d STK19 phosphorylates and activates oncogenic NRAS to promote melanomagenesis d We developed a novel potent and selective STK19 inhibitor, ZT-12-037-01 (1a) d ZT-12-037-01 (1a) inhibits NRAS-driven melanomagenesis and melanoma growth

BACKGROUND & AIMS Variants in genes that regulate autophagy have been associated with Crohn’s disease (CD). Defects in autophagy-mediated removal of pathogenic microbes could contribute to pathogenesis of CD. We investigated the role of the micro-RNAs (miRs) MIR106B and MIR93 in induction of autophagy and bacterial clearance in human cell lines, and the correlation between MIR106B and autophagy-related gene 16L1 (ATG16L1) expression in tissues from patients with CD. METHODS We studied the ability of MIR106B and MIR93 to regulate ATG transcripts in human cancer cell lines (HCT116, SW480, HeLa, and U2OS) using luciferase report assays and bioinformatics analyses; MIR106B and MIR93 mimics and antagonists were transfected into cells to modify levels of miRs. Cells were infected with LF82, a CD-associated adherent-invasive strain of Escherichia coli, and monitored by confocal microscopy and for colony-forming units. Colon tissues from 41 healthy individuals (controls), 22 with active CD, 16 with inactive CD, and 7 with chronic inflammation were assessed for levels of MIR106B and ATG16L1 by in situ hybridization and immunohistochemistry. RESULTS Silencing Dicer 1, an essential processor of miRs, increased levels of ATG protein and formation of autophagosomes in cells, indicating that miRs regulate autophagy. Luciferase reporter assays indicated that MIR106B and MIR93 targeted ATG16L1 mRNA. MIR106B and MIR93 reduced levels of ATG16L1 and autophagy; these increased following expression of ectopic ATG16L1. In contrast, MIR106B and MIR93 antagonists increased formation of autophagosomes. Levels of MIR106B were increased in intestinal epithelia from patients with active CD, whereas levels of ATG16L1 were reduced, compared with controls. Levels of CMYC were also increased in intestinal epithelia of patients with active CD, compared with controls. These alterations could impair removal of CD-associated bacteria by autophagy. CONCLUSIONS In human cell lines, MIR106B and MIR93 reduce levels of ATG16L1 and autophagy, and prevent autophagy-dependent eradication of intracellular bacteria. This process also appears to be altered in colon tissues from patients with active CD.

High-risk human papillomaviruses (HPVs) are causative agents of anogenital cancers and a fraction of head and neck cancers. The mechanisms involved in the progression of HPV neoplasias to cancers remain largely unknown. Here, we report that O-linked GlcNAcylation (O-GlcNAc) and O-GlcNAc transferase (OGT) were markedly increased in HPV-caused cervical neoplasms relative to normal cervix, whereas O-GlcNAcase (OGA) levels were not altered. Transduction of HPV16 oncogene E6 or E6/E7 into mouse embryonic fibroblasts (MEFs) up-regulated OGT mRNA and protein, elevated the level of O-GlcNAc, and promoted cell proliferation while reducing cellular senescence. Two HR HPV genes, E6 and E7, are potent oncogenes based on their immortalizing and transforming activities in cell culture systems and their capacities to induce tumors in animal models. The HR HPV E7 oncoprotein binds to more than 20 cellular targets and interferes with multiple cellular processes, leading to deregulated cell cycle, centrosome amplification, DNA damage, anoikis resistance, anchorage-independent cell growth and malignant transformation as well as immune surveillance evasion.