title: Increases in intracellular calcium dephosphorylate histone H3 at serine 10 in human hepatoma cells: potential role of protein phosphatase 2A-protein kinase CbetaII complex.
abstract: We present evidence that increases in intracellular calcium, induced by treatment with calcium ionophore A23187 or the endoplasmic reticulum calcium-ATPase inhibitor thapsigargin, dephosphorylated histone H3 at serine10 (histone H3-Ser10) in a dose-dependent manner in human hepatoma HepG2 cells. Inhibition of p42/44MAPK, pp90RSK, or p38MAPK did not affect the ability of A23187 to dephosphorylate histone H3-Ser10. This response is significantly blocked by okadaic acid, indicating a requirement for protein phosphatase 2A (PP2A). A23187 increased the activity of PP2A towards phosphorylated histone H3-Ser10. Furthermore, pretreatment with calphostin C, a selective protein kinase C (PKC) inhibitor, blocked A23187-dependent dephosphorylation of histone H3-Ser10, and coimmunoprecipitation analysis showed PP2A association with the PKCbetaII isoform. Unlike untreated cells, coimmunoprecipitated complex from A23187-treated cells showed greater dephosphorylation of histone H3-Ser10 in a PP2A-dependent manner. Inhibition of PP2A increased phosphorylation at Ser660 that determines calcium sensitivity and activity of PKCbetaII isoform, thus supporting a role for intracomplex regulation. Finally, chromatin immunoprecipitation assays following exposure to A23187 and okadaic acid revealed regulatory role of histone H3-Ser10 phosphorylation in selective gene induction. Altogether, our findings suggest a novel role for calcium in modulating histone H3-Ser10 phosphorylation level and led us to propose a model emphasizing PP2A activation, occurring downstream following perturbations in calcium homeostasis, as key event in dephosphorylating histone H3-Ser10 in mammalian cells.
authors.affiliation: Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine and Public Health, Columbus, Ohio 43210, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Sanjay
authors.initials: S
authors.lastname: Batra
authors.forename: Brett A
authors.initials: BA
authors.lastname: Atkins
authors.forename: Vachaspati
authors.initials: V
authors.lastname: Mishra
authors.forename: Kamal D
authors.initials: KD
authors.lastname: Mehta
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D006657:Histones / Q000378:metabolism*; D006801:Humans; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D064546:Protein Kinase C beta; D054648:Protein Phosphatase 2; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D006657:Histones; D011973:Receptors, LDL; D010768:Phosphoserine; D019319:Okadaic Acid; D000001:Calcimycin; D019284:Thapsigargin; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D002118:Calcium