References 1. Liu J, Lin A (2005) Role of JNK activation in apoptosis: a double-edged sword. Cell Res 15: 36–42. 2. Kwan R, Burnside J, Kurosaki T, Cheng G (2001) MEKK1 is essential for DT40 cell apoptosis in response to microtubule disruption. Mol Cell Biol 21: 7183–7190. 3. Rowinsky EK, Donehower RC (1991) The clinical pharmacology and use of antimicrotubule agents in cancer chemotherapeutics. Pharmacol Ther 52: 35–84. 4. Cardoso F, Bedard PL, Winer EP, Pagani O, Senkus-Konefka E, et al. (2009) International guidelines for management of metastatic breast cancer: combina- tion vs sequential single-agent chemotherapy. J Natl Cancer Inst 101: 1174–1181. 5. Kan Z, Jaiswal BS, Stinson J, Janakiraman V, Bhatt D, et al. Diverse somatic mutation patterns and pathway alterations in human cancers. Nature 466: 869–873. 6. Yujiri T, Fanger GR, Garrington TP, Schlesinger TK, Gibson S, et al. (1999) MEK kinase 1 (MEKK1) transduces c-Jun NH2-terminal kinase activation in response to changes in the microtubule cytoskeleton. J Biol Chem 274: 12605–12610. 7. Zhao B, Sun L, Haas M, Denenberg AG, Wong HR, et al. (2007) Pp2a Regulates Upstream Members of the C-Jun N-Terminal Kinase Mitogen- Activated Protein Kinase Signaling Pathway. Shock Publish Ahead of Print. 8. Cooper JA (1987) Effects of cytochalasin and phalloidin on actin. J Cell Biol 105: 1473–1478. 9. Strnad P, Windoffer R, Leube RE (2001) In vivo detection of cytokeratin filament network breakdown in cells treated with the phosphatase inhibitor okadaic acid. Cell Tissue Res 306: 277–293. 10. Schlesinger TK, Fanger GR, Yujiri T, Johnson GL (1998) The TAO of MEKK. Front Biosci 3: D1181–1186. 11. Lu Z, Xu S, Joazeiro C, Cobb MH, Hunter T (2002) The PHD domain of MEKK1 acts as an E3 ubiquitin ligase and mediates ubiquitination and degradation of ERK1/2. Mol Cell 9: 945–956. 12. Gallagher ED, Gutowski S, Sternweis PC, Cobb MH (2004) RhoA binds to the amino terminus of MEKK1 and regulates its kinase activity. J Biol Chem 279: 1872–1877. 13. Xia Y, Wang J, Xu S, Johnson GL, Hunter T, et al. (2006) MEKK1 Mediates the Ubiquitination and Degradation of c-Jun in Response to Osmotic Stress. Mol Cell Biol. 14. Witowsky JA, Johnson GL (2003) Ubiquitylation of MEKK1 inhibits its phosphorylation of MKK1 and MKK4 and activation of the ERK1/2 and JNK pathways. J Biol Chem 278: 1403–1406. 15. Gallagher E, Enzler T, Matsuzawa A, Anzelon-Mills A, Otero D, et al. (2007) Kinase MEKK1 is required for CD40-dependent activation of the kinases Jnk and p38, germinal center formation, B cell proliferation and antibody production. Nat Immunol 8: 57–63. 16. Hurley JH, Lee S, Prag G (2006) Ubiquitin-binding domains. Biochem J 399: 361–372. 17. Widmann C, Gerwins P, Johnson NL, Jarpe MB, Johnson GL (1998) MEK kinase 1, a substrate for DEVD-directed caspases, is involved in genotoxin- induced apoptosis. Mol Cell Biol 18: 2416–2429. 18. Chen YR, Wang X, Templeton D, Davis RJ, Tan TH (1996) The role of c-Jun N-terminal kinase (JNK) in apoptosis induced by ultraviolet C and gamma radiation. Duration of JNK activation may determine cell death and proliferation. J Biol Chem 271: 31929–31936. 19. Yujiri T, Sather S, Fanger GR, Johnson GL (1998) Role of MEKK1 in cell survival and activation of JNK and ERK pathways defined by targeted gene disruption. Science 282: 1911–1914. 20. Cardone MH, Salvesen GS, Widmann C, Johnson G, Frisch SM (1997) The regulation of anoikis: MEKK-1 activation requires cleavage by caspases. Cell 90: 315–323. MEKK1-Dependent Apoptosis Requires the PHD 21. Schlesinger TK, Bonvin C, Jarpe MB, Fanger GR, Cardinaux JR, et al. (2002) Apoptosis stimulated by the 91-kDa caspase cleavage MEKK1 fragment requires translocation to soluble cellular compartments. J Biol Chem 277: 10283–10291. 22. Deak JC, Templeton DJ (1997) Regulation of the activity of MEK kinase 1 (MEKK1) by autophosphorylation within the kinase activation domain. Biochem J 322(Pt 1): 185–192. 23. Matsuzawa ATP, Vallabhapurapu S, Luo JL, Zhang W, Wang H, Vignali DA, Gallagher E, Karin M (Science. 2008 Aug 1;321(5889):663–8. Epub 2008 Jul 17.) Essential cytoplasmic translocation of a cytokine receptor-assembled signaling complex. Science 321: 663–668. 24. Yujiri T, Ware M, Widmann C, Oyer R, Russell D, et al. (2000) MEK kinase 1 gene disruption alters cell migration and c-Jun NH2-terminal kinase regulation but does not cause a measurable defect in NF-kappa B activation. Proc Natl Acad Sci U S A 97: 7272–7277. 25. Giannini AL, Gao Y, Bijlmakers MJ (2008) T-cell regulator RNF125/TRAC-1 belongs to a novel family of ubiquitin ligases with zinc fingers and a ubiquitin- binding domain. Biochem J 410: 101–111. 26. Wang H, Matsuzawa A, Brown SA, Zhou J, Guy CS, et al. (2008) Analysis of nondegradative protein ubiquitylation with a monoclonal antibody specific for lysine-63-linked polyubiquitin. Proc Natl Acad Sci U S A 105: 20197–20202. 27. Miller SL ME, O’Bryan JP (2004) Analysis of the role of ubiquitin-interacting motifs in ubiquitin binding and ubiquitylation. J Biol Chem 279: 33528–33537. 28. Kolomeichuk SN, Terrano DT, Lyle CS, Sabapathy K, Chambers TC (2008) Distinct signaling pathways of microtubule inhibitors–vinblastine and Taxol induce JNK-dependent cell death but through AP-1-dependent and AP-1- independent mechanisms, respectively. Febs J 275: 1889–1899. 29. Chu R, Upreti M, Ding WX, Yin XM, Chambers TC (2009) Regulation of Bax by c-Jun NH2-terminal kinase and Bcl-xL in vinblastine-induced apoptosis. Biochem Pharmacol 78: 241–248. 30. Kolomeichuk SN, Bene A, Upreti M, Dennis RA, Lyle CS, et al. (2008) Induction of apoptosis by vinblastine via c-Jun autoamplification and p53- independent down-regulation of p21WAF1/CIP1. Mol Pharmacol 73: 128–136. 31. Chang L, Kamata H, Solinas G, Luo JL, Maeda S, et al. (2006) The E3 ubiquitin ligase itch couples JNK activation to TNFalpha-induced cell death by inducing c-FLIP(L) turnover. Cell 124: 601–613. 32. Ventura JJ, Hubner A, Zhang C, Flavell RA, Shokat KM, et al. (2006) Chemical genetic analysis of the time course of signal transduction by JNK. Mol Cell 21: 701–710. 33. White SR, Williams P, Wojcik KR, Sun S, Hiemstra PS, et al. (2001) Initiation of apoptosis by actin cytoskeletal derangement in human airway epithelial cells. Am J Respir Cell Mol Biol 24: 282–294. 34. Suria H, Chau LA, Negrou E, Kelvin DJ, Madrenas J (1999) Cytoskeletal disruption induces T cell apoptosis by a caspase-3 mediated mechanism. Life Sci 65: 2697–2707. 35. Chao JI, Liu HF (2006) The blockage of survivin and securin expression increases the cytochalasin B-induced cell death and growth inhibition in human cancer cells. Mol Pharmacol 69: 154–164. 36. Boudreau RT, Conrad DM, Hoskin DW (2007) Differential involvement of reactive oxygen species in apoptosis caused by the inhibition of protein phosphatase 2A in Jurkat and CCRF-CEM human T-leukemia cells. Exp Mol Pathol. 37. Boudreau RT, Conrad DM, Hoskin DW (2007) Apoptosis induced by protein phosphatase 2A (PP2A) inhibition in T leukemia cells is negatively regulated by PP2A-associated p38 mitogen-activated protein kinase. Cell Signal 19: 139–151. 38. McLaughlin J, Chianese E, Witte ON (1987) In vitro transformation of immature hematopoietic cells by the P210 BCR/ABL oncogene product of the Philadelphia chromosome. Proc Natl Acad Sci U S A 84: 6558–6562. 39. Nicoletti I, Migliorati G, Pagliacci MC, Grignani F, Riccardi C (1991) A rapid and simple method for measuring thymocyte apoptosis by propidium iodide staining and flow cytometry. J Immunol Methods 139: 271–279. PLoS ONE | www.plosone.org 12 February 2011 | Volume 6 | Issue 2 | e17310