title: TIPRL Inhibits Protein Phosphatase 4 Activity and Promotes H2AX Phosphorylation in the DNA Damage Response.
abstract: Despite advances in our understanding of protein kinase regulation in the DNA damage response, the mechanism that controls protein phosphatase activity in this pathway is unclear. Unlike kinases, the activity and specificity of serine/threonine phosphatases is governed largely by their associated proteins. Here we show that Tip41-like protein (TIPRL), an evolutionarily conserved binding protein for PP2A-family phosphatases, is a negative regulator of protein phosphatase 4 (PP4). Knockdown of TIPRL resulted in increased PP4 phosphatase activity and formation of the active PP4-C/PP4R2 complex known to dephosphorylate γ-H2AX. Thus, overexpression of TIPRL promotes phosphorylation of H2AX, and increases γ-H2AX positive foci in response to DNA damage, whereas knockdown of TIPRL inhibits γ-H2AX phosphorylation. In correlation with γ-H2AX levels, we found that TIPRL overexpression promotes cell death in response to genotoxic stress, and knockdown of TIPRL protects cells from genotoxic agents. Taken together, these data demonstrate that TIPRL inhibits PP4 activity to allow for H2AX phosphorylation and the subsequent DNA damage response.
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Kimberly Romero
authors.initials: KR
authors.lastname: Rosales
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Reid
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Thai Q
authors.initials: TQ
authors.lastname: Tran
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Wen-I
authors.initials: WI
authors.lastname: Wang
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Xazmin
authors.initials: X
authors.lastname: Lowman
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Min
authors.initials: M
authors.lastname: Pan
authors.affiliation: Department of Cancer Biology, Beckman Research Institute of City of Hope Cancer Center, Duarte, California, United States of America.
authors.forename: Mei
authors.initials: M
authors.lastname: Kong
mesh_terms: D016475:3T3 Cells; D000818:Animals; D016923:Cell Death; D004249:DNA Damage; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D006657:Histones; D047908:Intracellular Signaling Peptides and Proteins; D010749:Phosphoprotein Phosphatases; C468783:H2AX protein, human; C577326:TIPRL protein, human; C000609006:TIPRL protein, mouse; C080406:protein phosphatase 4; C475961:gamma-H2AX protein, mouse