title: Stress-induced phosphorylation of Thr486 in c-Myb by p38 mitogen-activated protein kinases attenuates conjugation of SUMO-2/3.
abstract: c-Myb plays an essential role in regulation of properly balanced hematopoiesis through transcriptional regulation of genes directly controlling cellular processes such as proliferation, differentiation, and apoptosis. The transcriptional activity and protein levels of c-Myb are strictly controlled through post-translational modifications such as phosphorylation, acetylation, ubiquitination, and SUMOylation. Conjugation of small ubiquitin-like modifier (SUMO) proteins has been shown to suppress the transcriptional activity of c-Myb. SUMO-1 modifies c-Myb under physiological conditions, whereas SUMO-2/3 conjugation was reported in cells under stress. Because stress also activates several cellular protein kinases, we investigated whether phosphorylation of c-Myb changes in stressed cells and whether a mutual interplay exists between phosphorylation and SUMOylation of c-Myb. Here we show that several types of environmental stress induce a rapid change in c-Myb phosphorylation. Interestingly, the phosphorylation of Thr(486), located in close proximity to SUMOylation site Lys(499) of c-Myb, is detected preferentially in nonSUMOylated protein and has a negative effect on stress-induced SUMOylation of c-Myb. Stress-activated p38 MAPKs phosphorylate Thr(486) in c-Myb, attenuate its SUMOylation, and increase its proteolytic turnover. Stressed cells expressing a phosphorylation-deficient T486A mutant demonstrate decreased expression of c-Myb target genes Bcl-2 and Bcl-xL and accelerated apoptosis because of increased SUMOylation of the mutant protein. These results suggest that phosphorylation-dependent modulation of c-Myb SUMOylation may be important for proper response of cells to stress. In summary, we have identified a novel regulatory interplay between phosphorylation and SUMOylation of c-Myb that regulates its activity in stressed cells.
authors.affiliation: From the Laboratory of Cellular Oncology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Juraj
authors.initials: J
authors.lastname: Bies
authors.forename: Marek
authors.initials: M
authors.lastname: Sramko
authors.forename: Linda
authors.initials: L
authors.lastname: Wolff
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D019556:COS Cells; D002522:Chlorocebus aethiops; D006801:Humans; D051379:Mice; D020125:Mutation, Missense; D010766:Phosphorylation / Q000502:physiology; D020598:Proto-Oncogene Proteins c-myb / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology*; D058207:Sumoylation / Q000502:physiology*; D013912:Threonine; D014452:Ubiquitins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051020:bcl-X Protein / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; D020598:Proto-Oncogene Proteins c-myb; C117909:SUMO2 protein, human; C515972:SUMO2 protein, mouse; C492189:SUMO3 protein, human; D025841:Small Ubiquitin-Related Modifier Proteins; C117908:Sumo3 protein, mouse; D014452:Ubiquitins; D051020:bcl-X Protein; D013912:Threonine; D048051:p38 Mitogen-Activated Protein Kinases
keywords: Apoptosis; Myb; Phosphorylation; Protein Degradation; Protein Stability; Stress; Sumoylation; Transcription; p38 MAPK