title: Tip60-mediated acetylation activates transcription independent apoptotic activity of Abl.
abstract: BACKGROUND
  The proto-oncogene, c-Abl encodes a ubiquitously expressed tyrosine kinase that critically governs the cell death response induced by genotoxic agents such as ionizing radiation and cisplatin. The catalytic function of Abl, which is essential for executing DNA damage response (DDR), is normally tightly regulated but upregulated several folds upon IR exposure due to ATM-mediated phosphorylation on S465. However, the mechanism/s leading to activation of Abl's apoptotic activity is currently unknown.
  
  
  RESULTS
  We investigated the role of acetyl modification in regulating apoptotic activity of Abl and the results showed that DNA strand break-inducing agents, ionizing radiation and bleomycin induced Abl acetylation. Using mass spectrophotometry and site-specific acetyl antibody, we identified Abl K921, located in the DNA binding domain, and conforming to one of the lysine residue in the consensus acetylation motif (KXXK--X3-5--SGS) is acetylated following DNA damage. We further observed that the S465 phosphorylated Abl is acetyl modified during DNA damage. Signifying the modification, cells expressing the non acetylatable K921R mutant displayed attenuated apoptosis compared to wild-type in response to IR or bleomycin treatment. WT-Abl induced apoptosis irrespective of new protein synthesis. Furthermore, upon γ-irradiation K921R-Abl displayed reduced chromatin binding compared to wild type. Finally, loss of Abl K921 acetylation in Tip60-knocked down cells and co-precipitation of Abl with Tip60 in DNA damaged cells identified Tip60 as an Abl acetylase.
  
  
  CONCLUSIONS
  Collective data showed that DNA damage-induced K921 Abl acetylation, mediated by Tip60, stimulates transcriptional-independent apoptotic activity and chromatin-associative property thereby defining a new regulatory mechanism governing Abl's DDR function.
authors.affiliation: Department of Microbiology and Molecular Genetics, Pittsburgh, PA 15240, USA.
authors.forename: Zhihua
authors.initials: Z
authors.lastname: Jiang
authors.forename: Ravindra
authors.initials: R
authors.lastname: Kamath
authors.forename: Shunquian
authors.initials: S
authors.lastname: Jin
authors.forename: Manimalha
authors.initials: M
authors.lastname: Balasubramani
authors.forename: Tej K
authors.initials: TK
authors.lastname: Pandita
authors.forename: Baskaran
authors.initials: B
authors.lastname: Rajasekaran
mesh_terms: D016475:3T3 Cells; D000107:Acetylation; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D002478:Cells, Cultured; D045325:HCT116 Cells; D006367:HeLa Cells; D051548:Histone Acetyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D000074443:Lysine Acetyltransferase 5; D051379:Mice; D016374:Oncogene Proteins v-abl / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D000090063:Proto-Oncogene Mas; D034741:RNA, Small Interfering / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics / Q000502:physiology
chemical_list: C000715470:MAS1 protein, human; D016374:Oncogene Proteins v-abl; D000090063:Proto-Oncogene Mas; D034741:RNA, Small Interfering; D051548:Histone Acetyltransferases; C098489:KAT5 protein, human; D000074443:Lysine Acetyltransferase 5