title: HEY1 functions are regulated by its phosphorylation at Ser-68.
abstract: HEY1 (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.
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain.
authors.forename: Irene
authors.initials: I
authors.lastname: López-Mateo
authors.affiliation: Proteomics Unit, CIC bioGUNE, Bizkaia Technology Park, 48160 Derio, Spain.
authors.forename: Amaia
authors.initials: A
authors.lastname: Arruabarrena-Aristorena
authors.affiliation: División de Inmunología, Centro de Investigación Biomédica de Occidente-IMSS, Sierra Mojada 800, 44340 Guadalajara, Jalisco, Mexico.
authors.forename: Cristina
authors.initials: C
authors.lastname: Artaza-Irigaray
authors.affiliation: Unidad de Proteomica, Centro Nacional de Investigaciones Cardiovasculares, CNIC, 28029 Madrid, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: López
authors.affiliation: Unidad de Proteomica, Centro Nacional de Investigaciones Cardiovasculares, CNIC, 28029 Madrid, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Calvo
authors.affiliation: Department of Cancer Biology, Instituto de Investigaciones Biomédicas Alberto Sols, CSIC-UAM, Arturo Duperier 4, 28029 Madrid, Spain bbelandia@iib.uam.es.
authors.forename: Borja
authors.initials: B
authors.lastname: Belandia
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D059447:Cell Cycle Checkpoints / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D059748:Proteolysis; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D051880:Receptors, Notch / Q000235:genetics; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D017346:Protein Serine-Threonine Kinases; D051736:Proto-Oncogene Proteins c-mdm2; D051880:Receptors, Notch; D012269:Ribosomal Proteins; D012694:Serine; D016159:Tumor Suppressor Protein p53; C485631:HEY1 protein, human; C495901:TP53 protein, human; C027624:ribosomal protein L11; C497206:MDM2 protein, human; C491614:STK38 protein, human; C496014:STK38L protein, human
keywords: HEY1; STK38; centrosome; p53; phosphorylation; ribosomal stress