HEY1 functions are regulated by its phosphorylation at Ser-68

Abstract

SynopsisHEY1 (hairy/enhancer-of-split related with YRPW motif 1) is a member of the basic helix-loop-helix-orange (bHLH-O) family of transcription repressors that mediate Notch signalling. HEY1 acts as a positive regulator of the tumour suppressor p53 via still unknown mechanisms. A MALDI-TOF/TOF MS analysis has uncovered a novel HEY1 regulatory phosphorylation event at Ser-68. Strikingly, this single phosphorylation event controls HEY1 stability and function: simulation of HEY1 Ser-68 phosphorylation increases HEY1 protein stability but inhibits its ability to enhance p53 transcriptional activity. Unlike wild-type HEY1, expression of the phosphomimetic mutant HEY1-S68D failed to induce p53-dependent cell cycle arrest and it did not sensitize U2OS cells to p53-activating chemotherapeutic drugs. We have identified two related kinases, STK38 (serine/threonine kinase 38) and STK38L (serine/threonine kinase 38 like), which interact with and phosphorylate HEY1 at Ser-68. HEY1 is phosphorylated at Ser-68 during mitosis and it accumulates in the centrosomes of mitotic cells, suggesting a possible integration of HEY1-dependent signalling in centrosome function. Moreover, HEY1 interacts with a subset of p53-activating ribosomal proteins. Ribosomal stress causes HEY1 relocalization from the nucleoplasm to perinucleolar structures termed nucleolar caps. HEY1 interacts physically with at least one of the ribosomal proteins, RPL11, and both proteins cooperate in the inhibition of MDM2-mediated p53 degradation resulting in a synergistic positive effect on p53 transcriptional activity. HEY1 itself also interacts directly with MDM2 and it is subjected to MDM2-mediated degradation. Simulation of HEY1 Ser-68 phosphorylation prevents its interaction with p53, RPL11 and MDM2 and abolishes HEY1 migration to nucleolar caps upon ribosomal stress. Our findings uncover a novel mechanism for cross-talk between Notch signalling and nucleolar stress.

MicroRNA‑145‑5p attenuates high glucose‑induced apoptosis by targeting the Notch signaling pathway in podocytes

“…Overexpression of miR-145-5p suppresses HG-induced activation of the Notch signaling pathway. The Notch signaling pathway contains numerous effectors, including NICD, Hes1 and Hey1 (30)(31)(32). To further determine the effect of miR-145-5p on the Notch signaling pathway, the present study detected the expression levels of NICD, Hes1 and Hey1, which are important downstream factors of this signaling pathway.…”

Impaired Notch Signaling Leads to a Decrease in p53 Activity and Mitotic Catastrophe in Aged Muscle Stem Cells

“…The mechanism by which Notch activation induces p53-dependent transcription in these conditions remains unknown. In human sarcoma cells, expression of the canonical Notch target gene Hey1 has an inhibitory effect on Mdm2-mediated p53 degradation and sensitizes cells to chemotherapeutic drugs (Lopez-Mateo et al, 2016). A model has been put forth that Hey1 competes with p53 for binding with Mdm2 thereby suppressing the Mdm2-mediated p53 degradation.…”

Large‐conductance Ca2+‐activated K+ channel activation by apical P2Y receptor agonists requires hydrocortisone in differentiated airway epithelium

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