The ULK3 kinase is a determinant of keratinocyte self-renewal and tumorigenesis targeting the arginine methylome

Abstract

Epigenetic mechanisms oversee epidermal homeostasis and oncogenesis. The identification of kinases controlling these processes has direct therapeutic implications. We show that ULK3 is a nuclear kinase with elevated expression levels in squamous cell carcinomas (SCCs) arising in multiple body sites, including skin and Head/Neck. ULK3 loss by gene silencing or deletion reduces proliferation and clonogenicity of human keratinocytes and SCC-derived cells and affects transcription impinging on stem cell-related and metabolism programs. Mechanistically, ULK3 directly binds and regulates the activity of two histone arginine methyltransferases, PRMT1 and PRMT5 (PRMT1/5), with ULK3 loss compromising PRMT1/5 chromatin association to specific genes and overall methylation of histone H4, a shared target of these enzymes. These findings are of translational significance, as downmodulating ULK3 by RNA interference or locked antisense nucleic acids (LNAs) blunts the proliferation and tumorigenic potential of SCC cells and promotes differentiation in two orthotopic models of skin cancer.

Identifying actionable druggable targets for breast cancer: Mendelian randomization and population-based analyses

“…Extensive clinical data suggest that the expression levels of ULK3 are heightened in squamous cell carcinomas of the lung, head and neck, and cervix. 29 MC1R encodes the receptor protein for melanocyte-stimulating hormone and thus plays a pivotal role in pigmentation. The activation of MC1R could upregulate cAMP signaling, boost the production of melanin, and improve DNA repair following exposure to ultraviolet radiation.…”

Pro‐inflammatory cytokine IL‐6 regulates LMO4 expression in psoriatic keratinocytes via AKT/STAT3 pathway

“…Edu, structurally similar to the natural nucleoside, can be coupled via click chemistry. The small sized dye‐azide allows for efficient EdU detection upon incorporation 38,39 . HaCaT cells were treated with phosphate‐buffered saline (PBS), IL‐6 (15 ng/mL), or IL‐6 (15 ng/mL) plus inhibitors (AG490: 10 μM; MK‐2206: 10 μM; NSC 74859: 80 μM) for 21 h, and then incubated with 10 μM EdU for 3 h in a CO 2 incubator at 37℃.…”

“…The small sized dye-azide allows for efficient EdU detection upon incorporation. 38,39 HaCaT cells were treated with phosphate-buffered saline (PBS), IL-6 (15 ng/mL), or IL-6 (15 ng/mL) plus inhibitors (AG490: 10 μM; MK-2206: 10 μM; NSC 74859: 80 μM) for 21 h, and then incubated with 10 μM EdU for 3 h in a CO 2 incubator at 37℃. Cells were collected using 0.25% trypsin, fixed with 4% paraformaldehyde, permeabilized with 0.3% Triton X-100, and stained with a click reaction solution protected from light for 30 min.…”

Protein arginine methylation in viral infection and antiviral immunity

“…In contrast, Unc51-like kinase 3 (ULK3) interacts with and phosphorylates PRMT1 to enhance its methyltransferase activity and promote chromatin recruitment. This, in turn, increases H4R3 methylation and cell proliferation, leading to the tumorigenic differentiation of epidermal keratinocytes, ultimately facilitating epidermal oncogenesis 86 (Figure 3 D). Notably, PRMT1 phosphorylation at Y291 impairs its ability to methylate substrates, resulting in altered substrate specificity and protein interactions 87 .…”

“…PRMT5-mediated histone H4R3me2s methylation is also regulated by phosphorylation. For instance, ULK3 phosphorylates PRMT5, in addition to PRMT1, to enhance its recruitment to chromatin and H4R3me2s methylation, thereby preventing oncogenesis and tumorigenic differentiation of keratinocytes 86 . In contrast, RhoA activating kinase (ROK) phosphorylates PRMT5 at T80 enhancing its activity on H4R3me2s and activating proto-oncogenes, contributing to tumor formation in hepatocellular carcinoma.…”