Skip to main content
PMC home page
Molecular and Cellular Biology logoLink to Molecular and Cellular Biology
. 1995 Oct;15(10):5214–5225. doi: 10.1128/mcb.15.10.5214

A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function.

A D Catling 1, H J Schaeffer 1, C W Reuter 1, G R Reddy 1, M J Weber 1
PMCID: PMC230769  PMID: 7565670

Abstract

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

Full Text

The Full Text of this article is available as a PDF (1.0 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Alessi D. R., Saito Y., Campbell D. G., Cohen P., Sithanandam G., Rapp U., Ashworth A., Marshall C. J., Cowley S. Identification of the sites in MAP kinase kinase-1 phosphorylated by p74raf-1. EMBO J. 1994 Apr 1;13(7):1610–1619. doi: 10.1002/j.1460-2075.1994.tb06424.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Ambrosio L., Mahowald A. P., Perrimon N. Requirement of the Drosophila raf homologue for torso function. Nature. 1989 Nov 16;342(6247):288–291. doi: 10.1038/342288a0. [DOI] [PubMed] [Google Scholar]
  3. Anderson N. G., Maller J. L., Tonks N. K., Sturgill T. W. Requirement for integration of signals from two distinct phosphorylation pathways for activation of MAP kinase. Nature. 1990 Feb 15;343(6259):651–653. doi: 10.1038/343651a0. [DOI] [PubMed] [Google Scholar]
  4. Boyle W. J., van der Geer P., Hunter T. Phosphopeptide mapping and phosphoamino acid analysis by two-dimensional separation on thin-layer cellulose plates. Methods Enzymol. 1991;201:110–149. doi: 10.1016/0076-6879(91)01013-r. [DOI] [PubMed] [Google Scholar]
  5. Brunet A., Pagès G., Pouysségur J. Growth factor-stimulated MAP kinase induces rapid retrophosphorylation and inhibition of MAP kinase kinase (MEK1). FEBS Lett. 1994 Jun 13;346(2-3):299–303. doi: 10.1016/0014-5793(94)00475-7. [DOI] [PubMed] [Google Scholar]
  6. Burgering B. M., de Vries-Smits A. M., Medema R. H., van Weeren P. C., Tertoolen L. G., Bos J. L. Epidermal growth factor induces phosphorylation of extracellular signal-regulated kinase 2 via multiple pathways. Mol Cell Biol. 1993 Dec;13(12):7248–7256. doi: 10.1128/mcb.13.12.7248. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Catling A. D., Reuter C. W., Cox M. E., Parsons S. J., Weber M. J. Partial purification of a mitogen-activated protein kinase kinase activator from bovine brain. Identification as B-Raf or a B-Raf-associated activity. J Biol Chem. 1994 Nov 25;269(47):30014–30021. [PubMed] [Google Scholar]
  8. Cobb M. H., Boulton T. G., Robbins D. J. Extracellular signal-regulated kinases: ERKs in progress. Cell Regul. 1991 Dec;2(12):965–978. doi: 10.1091/mbc.2.12.965. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Cohen G. B., Ren R., Baltimore D. Modular binding domains in signal transduction proteins. Cell. 1995 Jan 27;80(2):237–248. doi: 10.1016/0092-8674(95)90406-9. [DOI] [PubMed] [Google Scholar]
  10. Cowley S., Paterson H., Kemp P., Marshall C. J. Activation of MAP kinase kinase is necessary and sufficient for PC12 differentiation and for transformation of NIH 3T3 cells. Cell. 1994 Jun 17;77(6):841–852. doi: 10.1016/0092-8674(94)90133-3. [DOI] [PubMed] [Google Scholar]
  11. Crews C. M., Alessandrini A., Erikson R. L. The primary structure of MEK, a protein kinase that phosphorylates the ERK gene product. Science. 1992 Oct 16;258(5081):478–480. doi: 10.1126/science.1411546. [DOI] [PubMed] [Google Scholar]
  12. Crews C. M., Erikson R. L. Extracellular signals and reversible protein phosphorylation: what to Mek of it all. Cell. 1993 Jul 30;74(2):215–217. doi: 10.1016/0092-8674(93)90411-i. [DOI] [PubMed] [Google Scholar]
  13. Davis R. J. The mitogen-activated protein kinase signal transduction pathway. J Biol Chem. 1993 Jul 15;268(20):14553–14556. [PubMed] [Google Scholar]
  14. Dent P., Chow Y. H., Wu J., Morrison D. K., Jove R., Sturgill T. W. Expression, purification and characterization of recombinant mitogen-activated protein kinase kinases. Biochem J. 1994 Oct 1;303(Pt 1):105–112. doi: 10.1042/bj3030105. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Dent P., Haser W., Haystead T. A., Vincent L. A., Roberts T. M., Sturgill T. W. Activation of mitogen-activated protein kinase kinase by v-Raf in NIH 3T3 cells and in vitro. Science. 1992 Sep 4;257(5075):1404–1407. doi: 10.1126/science.1326789. [DOI] [PubMed] [Google Scholar]
  16. Der C. J., Finkel T., Cooper G. M. Biological and biochemical properties of human rasH genes mutated at codon 61. Cell. 1986 Jan 17;44(1):167–176. doi: 10.1016/0092-8674(86)90495-2. [DOI] [PubMed] [Google Scholar]
  17. Dickson B., Sprenger F., Morrison D., Hafen E. Raf functions downstream of Ras1 in the Sevenless signal transduction pathway. Nature. 1992 Dec 10;360(6404):600–603. doi: 10.1038/360600a0. [DOI] [PubMed] [Google Scholar]
  18. Dérijard B., Hibi M., Wu I. H., Barrett T., Su B., Deng T., Karin M., Davis R. J. JNK1: a protein kinase stimulated by UV light and Ha-Ras that binds and phosphorylates the c-Jun activation domain. Cell. 1994 Mar 25;76(6):1025–1037. doi: 10.1016/0092-8674(94)90380-8. [DOI] [PubMed] [Google Scholar]
  19. Dérijard B., Raingeaud J., Barrett T., Wu I. H., Han J., Ulevitch R. J., Davis R. J. Independent human MAP-kinase signal transduction pathways defined by MEK and MKK isoforms. Science. 1995 Feb 3;267(5198):682–685. doi: 10.1126/science.7839144. [DOI] [PubMed] [Google Scholar]
  20. Errede B., Levin D. E. A conserved kinase cascade for MAP kinase activation in yeast. Curr Opin Cell Biol. 1993 Apr;5(2):254–260. doi: 10.1016/0955-0674(93)90112-4. [DOI] [PubMed] [Google Scholar]
  21. Finney R. E., Robbins S. M., Bishop J. M. Association of pRas and pRaf-1 in a complex correlates with activation of a signal transduction pathway. Curr Biol. 1993 Dec 1;3(12):805–812. doi: 10.1016/0960-9822(93)90214-9. [DOI] [PubMed] [Google Scholar]
  22. Force T., Bonventre J. V., Heidecker G., Rapp U., Avruch J., Kyriakis J. M. Enzymatic characteristics of the c-Raf-1 protein kinase. Proc Natl Acad Sci U S A. 1994 Feb 15;91(4):1270–1274. doi: 10.1073/pnas.91.4.1270. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Galcheva-Gargova Z., Dérijard B., Wu I. H., Davis R. J. An osmosensing signal transduction pathway in mammalian cells. Science. 1994 Aug 5;265(5173):806–808. doi: 10.1126/science.8047888. [DOI] [PubMed] [Google Scholar]
  24. Gómez N., Cohen P. Dissection of the protein kinase cascade by which nerve growth factor activates MAP kinases. Nature. 1991 Sep 12;353(6340):170–173. doi: 10.1038/353170a0. [DOI] [PubMed] [Google Scholar]
  25. Han J., Lee J. D., Bibbs L., Ulevitch R. J. A MAP kinase targeted by endotoxin and hyperosmolarity in mammalian cells. Science. 1994 Aug 5;265(5173):808–811. doi: 10.1126/science.7914033. [DOI] [PubMed] [Google Scholar]
  26. Han M., Golden A., Han Y., Sternberg P. W. C. elegans lin-45 raf gene participates in let-60 ras-stimulated vulval differentiation. Nature. 1993 May 13;363(6425):133–140. doi: 10.1038/363133a0. [DOI] [PubMed] [Google Scholar]
  27. Haystead C. M., Gregory P., Shirazi A., Fadden P., Mosse C., Dent P., Haystead T. A. Insulin activates a novel adipocyte mitogen-activated protein kinase kinase kinase that shows rapid phasic kinetics and is distinct from c-Raf. J Biol Chem. 1994 Apr 29;269(17):12804–12808. [PubMed] [Google Scholar]
  28. Heasley L. E., Johnson G. L. The beta-PDGF receptor induces neuronal differentiation of PC12 cells. Mol Biol Cell. 1992 May;3(5):545–553. doi: 10.1091/mbc.3.5.545. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Howe L. R., Leevers S. J., Gómez N., Nakielny S., Cohen P., Marshall C. J. Activation of the MAP kinase pathway by the protein kinase raf. Cell. 1992 Oct 16;71(2):335–342. doi: 10.1016/0092-8674(92)90361-f. [DOI] [PubMed] [Google Scholar]
  30. Huang W., Alessandrini A., Crews C. M., Erikson R. L. Raf-1 forms a stable complex with Mek1 and activates Mek1 by serine phosphorylation. Proc Natl Acad Sci U S A. 1993 Dec 1;90(23):10947–10951. doi: 10.1073/pnas.90.23.10947. [DOI] [PMC free article] [PubMed] [Google Scholar]
  31. Huang W., Erikson R. L. Constitutive activation of Mek1 by mutation of serine phosphorylation sites. Proc Natl Acad Sci U S A. 1994 Sep 13;91(19):8960–8963. doi: 10.1073/pnas.91.19.8960. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Hughes D. A., Ashworth A., Marshall C. J. Complementation of byr1 in fission yeast by mammalian MAP kinase kinase requires coexpression of Raf kinase. Nature. 1993 Jul 22;364(6435):349–352. doi: 10.1038/364349a0. [DOI] [PubMed] [Google Scholar]
  33. Jaiswal R. K., Moodie S. A., Wolfman A., Landreth G. E. The mitogen-activated protein kinase cascade is activated by B-Raf in response to nerve growth factor through interaction with p21ras. Mol Cell Biol. 1994 Oct;14(10):6944–6953. doi: 10.1128/mcb.14.10.6944. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Jelinek T., Catling A. D., Reuter C. W., Moodie S. A., Wolfman A., Weber M. J. RAS and RAF-1 form a signalling complex with MEK-1 but not MEK-2. Mol Cell Biol. 1994 Dec;14(12):8212–8218. doi: 10.1128/mcb.14.12.8212. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Kahan C., Seuwen K., Meloche S., Pouysségur J. Coordinate, biphasic activation of p44 mitogen-activated protein kinase and S6 kinase by growth factors in hamster fibroblasts. Evidence for thrombin-induced signals different from phosphoinositide turnover and adenylylcyclase inhibition. J Biol Chem. 1992 Jul 5;267(19):13369–13375. [PubMed] [Google Scholar]
  36. Kolch W., Heidecker G., Lloyd P., Rapp U. R. Raf-1 protein kinase is required for growth of induced NIH/3T3 cells. Nature. 1991 Jan 31;349(6308):426–428. doi: 10.1038/349426a0. [DOI] [PubMed] [Google Scholar]
  37. Kyriakis J. M., App H., Zhang X. F., Banerjee P., Brautigan D. L., Rapp U. R., Avruch J. Raf-1 activates MAP kinase-kinase. Nature. 1992 Jul 30;358(6385):417–421. doi: 10.1038/358417a0. [DOI] [PubMed] [Google Scholar]
  38. Kyriakis J. M., Banerjee P., Nikolakaki E., Dai T., Rubie E. A., Ahmad M. F., Avruch J., Woodgett J. R. The stress-activated protein kinase subfamily of c-Jun kinases. Nature. 1994 May 12;369(6476):156–160. doi: 10.1038/369156a0. [DOI] [PubMed] [Google Scholar]
  39. Kyriakis J. M., Brautigan D. L., Ingebritsen T. S., Avruch J. pp54 microtubule-associated protein-2 kinase requires both tyrosine and serine/threonine phosphorylation for activity. J Biol Chem. 1991 Jun 5;266(16):10043–10046. [PubMed] [Google Scholar]
  40. Kyriakis J. M., Force T. L., Rapp U. R., Bonventre J. V., Avruch J. Mitogen regulation of c-Raf-1 protein kinase activity toward mitogen-activated protein kinase-kinase. J Biol Chem. 1993 Jul 25;268(21):16009–16019. [PubMed] [Google Scholar]
  41. Lange-Carter C. A., Pleiman C. M., Gardner A. M., Blumer K. J., Johnson G. L. A divergence in the MAP kinase regulatory network defined by MEK kinase and Raf. Science. 1993 Apr 16;260(5106):315–319. doi: 10.1126/science.8385802. [DOI] [PubMed] [Google Scholar]
  42. Leevers S. J., Paterson H. F., Marshall C. J. Requirement for Ras in Raf activation is overcome by targeting Raf to the plasma membrane. Nature. 1994 Jun 2;369(6479):411–414. doi: 10.1038/369411a0. [DOI] [PubMed] [Google Scholar]
  43. Macdonald S. G., Crews C. M., Wu L., Driller J., Clark R., Erikson R. L., McCormick F. Reconstitution of the Raf-1-MEK-ERK signal transduction pathway in vitro. Mol Cell Biol. 1993 Nov;13(11):6615–6620. doi: 10.1128/mcb.13.11.6615. [DOI] [PMC free article] [PubMed] [Google Scholar]
  44. Mansour S. J., Matten W. T., Hermann A. S., Candia J. M., Rong S., Fukasawa K., Vande Woude G. F., Ahn N. G. Transformation of mammalian cells by constitutively active MAP kinase kinase. Science. 1994 Aug 12;265(5174):966–970. doi: 10.1126/science.8052857. [DOI] [PubMed] [Google Scholar]
  45. Mansour S. J., Resing K. A., Candi J. M., Hermann A. S., Gloor J. W., Herskind K. R., Wartmann M., Davis R. J., Ahn N. G. Mitogen-activated protein (MAP) kinase phosphorylation of MAP kinase kinase: determination of phosphorylation sites by mass spectrometry and site-directed mutagenesis. J Biochem. 1994 Aug;116(2):304–314. doi: 10.1093/oxfordjournals.jbchem.a124524. [DOI] [PubMed] [Google Scholar]
  46. Marshall C. J. Specificity of receptor tyrosine kinase signaling: transient versus sustained extracellular signal-regulated kinase activation. Cell. 1995 Jan 27;80(2):179–185. doi: 10.1016/0092-8674(95)90401-8. [DOI] [PubMed] [Google Scholar]
  47. Melnick M. B., Perkins L. A., Lee M., Ambrosio L., Perrimon N. Developmental and molecular characterization of mutations in the Drosophila-raf serine/threonine protein kinase. Development. 1993 May;118(1):127–138. doi: 10.1242/dev.118.1.127. [DOI] [PubMed] [Google Scholar]
  48. Minden A., Lin A., McMahon M., Lange-Carter C., Dérijard B., Davis R. J., Johnson G. L., Karin M. Differential activation of ERK and JNK mitogen-activated protein kinases by Raf-1 and MEKK. Science. 1994 Dec 9;266(5191):1719–1723. doi: 10.1126/science.7992057. [DOI] [PubMed] [Google Scholar]
  49. Moodie S. A., Paris M. J., Kolch W., Wolfman A. Association of MEK1 with p21ras.GMPPNP is dependent on B-Raf. Mol Cell Biol. 1994 Nov;14(11):7153–7162. doi: 10.1128/mcb.14.11.7153. [DOI] [PMC free article] [PubMed] [Google Scholar]
  50. Moodie S. A., Willumsen B. M., Weber M. J., Wolfman A. Complexes of Ras.GTP with Raf-1 and mitogen-activated protein kinase kinase. Science. 1993 Jun 11;260(5114):1658–1661. doi: 10.1126/science.8503013. [DOI] [PubMed] [Google Scholar]
  51. Neiman A. M., Stevenson B. J., Xu H. P., Sprague G. F., Jr, Herskowitz I., Wigler M., Marcus S. Functional homology of protein kinases required for sexual differentiation in Schizosaccharomyces pombe and Saccharomyces cerevisiae suggests a conserved signal transduction module in eukaryotic organisms. Mol Biol Cell. 1993 Jan;4(1):107–120. doi: 10.1091/mbc.4.1.107. [DOI] [PMC free article] [PubMed] [Google Scholar]
  52. Nguyen T. T., Scimeca J. C., Filloux C., Peraldi P., Carpentier J. L., Van Obberghen E. Co-regulation of the mitogen-activated protein kinase, extracellular signal-regulated kinase 1, and the 90-kDa ribosomal S6 kinase in PC12 cells. Distinct effects of the neurotrophic factor, nerve growth factor, and the mitogenic factor, epidermal growth factor. J Biol Chem. 1993 May 5;268(13):9803–9810. [PubMed] [Google Scholar]
  53. Osborne W. R., Hock R. A., Kaleko M., Miller A. D. Long-term expression of human adenosine deaminase in mice after transplantation of bone marrow infected with amphotropic retroviral vectors. Hum Gene Ther. 1990 Spring;1(1):31–41. doi: 10.1089/hum.1990.1.1-31. [DOI] [PubMed] [Google Scholar]
  54. Pagès G., Brunet A., L'Allemain G., Pouysségur J. Constitutive mutant and putative regulatory serine phosphorylation site of mammalian MAP kinase kinase (MEK1). EMBO J. 1994 Jul 1;13(13):3003–3010. doi: 10.1002/j.1460-2075.1994.tb06599.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  55. Pang L., Zheng C. F., Guan K. L., Saltiel A. R. Nerve growth factor stimulates a novel protein kinase in PC-12 cells that phosphorylates and activates mitogen-activated protein kinase kinase (MEK). Biochem J. 1995 Apr 15;307(Pt 2):513–519. doi: 10.1042/bj3070513. [DOI] [PMC free article] [PubMed] [Google Scholar]
  56. Payne D. M., Rossomando A. J., Martino P., Erickson A. K., Her J. H., Shabanowitz J., Hunt D. F., Weber M. J., Sturgill T. W. Identification of the regulatory phosphorylation sites in pp42/mitogen-activated protein kinase (MAP kinase). EMBO J. 1991 Apr;10(4):885–892. doi: 10.1002/j.1460-2075.1991.tb08021.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Posada J., Yew N., Ahn N. G., Vande Woude G. F., Cooper J. A. Mos stimulates MAP kinase in Xenopus oocytes and activates a MAP kinase kinase in vitro. Mol Cell Biol. 1993 Apr;13(4):2546–2553. doi: 10.1128/mcb.13.4.2546. [DOI] [PMC free article] [PubMed] [Google Scholar]
  58. Reuter C. W., Catling A. D., Jelinek T., Weber M. J. Biochemical analysis of MEK activation in NIH3T3 fibroblasts. Identification of B-Raf and other activators. J Biol Chem. 1995 Mar 31;270(13):7644–7655. doi: 10.1074/jbc.270.13.7644. [DOI] [PubMed] [Google Scholar]
  59. Rossomando A. J., Dent P., Sturgill T. W., Marshak D. R. Mitogen-activated protein kinase kinase 1 (MKK1) is negatively regulated by threonine phosphorylation. Mol Cell Biol. 1994 Mar;14(3):1594–1602. doi: 10.1128/mcb.14.3.1594. [DOI] [PMC free article] [PubMed] [Google Scholar]
  60. Rouse J., Cohen P., Trigon S., Morange M., Alonso-Llamazares A., Zamanillo D., Hunt T., Nebreda A. R. A novel kinase cascade triggered by stress and heat shock that stimulates MAPKAP kinase-2 and phosphorylation of the small heat shock proteins. Cell. 1994 Sep 23;78(6):1027–1037. doi: 10.1016/0092-8674(94)90277-1. [DOI] [PubMed] [Google Scholar]
  61. Saito Y., Gomez N., Campbell D. G., Ashworth A., Marshall C. J., Cohen P. The threonine residues in MAP kinase kinase 1 phosphorylated by MAP kinase in vitro are also phosphorylated in nerve growth factor-stimulated rat phaeochromocytoma (PC12) cells. FEBS Lett. 1994 Mar 14;341(1):119–124. doi: 10.1016/0014-5793(94)80252-1. [DOI] [PubMed] [Google Scholar]
  62. Samuels M. L., Weber M. J., Bishop J. M., McMahon M. Conditional transformation of cells and rapid activation of the mitogen-activated protein kinase cascade by an estradiol-dependent human raf-1 protein kinase. Mol Cell Biol. 1993 Oct;13(10):6241–6252. doi: 10.1128/mcb.13.10.6241. [DOI] [PMC free article] [PubMed] [Google Scholar]
  63. Schaap D., van der Wal J., Howe L. R., Marshall C. J., van Blitterswijk W. J. A dominant-negative mutant of raf blocks mitogen-activated protein kinase activation by growth factors and oncogenic p21ras. J Biol Chem. 1993 Sep 25;268(27):20232–20236. [PubMed] [Google Scholar]
  64. Stokoe D., Macdonald S. G., Cadwallader K., Symons M., Hancock J. F. Activation of Raf as a result of recruitment to the plasma membrane. Science. 1994 Jun 3;264(5164):1463–1467. doi: 10.1126/science.7811320. [DOI] [PubMed] [Google Scholar]
  65. Sturgill T. W., Wu J. Recent progress in characterization of protein kinase cascades for phosphorylation of ribosomal protein S6. Biochim Biophys Acta. 1991 May 17;1092(3):350–357. doi: 10.1016/s0167-4889(97)90012-4. [DOI] [PubMed] [Google Scholar]
  66. Sánchez I., Hughes R. T., Mayer B. J., Yee K., Woodgett J. R., Avruch J., Kyriakis J. M., Zon L. I. Role of SAPK/ERK kinase-1 in the stress-activated pathway regulating transcription factor c-Jun. Nature. 1994 Dec 22;372(6508):794–798. doi: 10.1038/372794a0. [DOI] [PubMed] [Google Scholar]
  67. Traverse S., Gomez N., Paterson H., Marshall C., Cohen P. Sustained activation of the mitogen-activated protein (MAP) kinase cascade may be required for differentiation of PC12 cells. Comparison of the effects of nerve growth factor and epidermal growth factor. Biochem J. 1992 Dec 1;288(Pt 2):351–355. doi: 10.1042/bj2880351. [DOI] [PMC free article] [PubMed] [Google Scholar]
  68. Tsuda L., Inoue Y. H., Yoo M. A., Mizuno M., Hata M., Lim Y. M., Adachi-Yamada T., Ryo H., Masamune Y., Nishida Y. A protein kinase similar to MAP kinase activator acts downstream of the raf kinase in Drosophila. Cell. 1993 Feb 12;72(3):407–414. doi: 10.1016/0092-8674(93)90117-9. [DOI] [PubMed] [Google Scholar]
  69. Vaillancourt R. R., Gardner A. M., Johnson G. L. B-Raf-dependent regulation of the MEK-1/mitogen-activated protein kinase pathway in PC12 cells and regulation by cyclic AMP. Mol Cell Biol. 1994 Oct;14(10):6522–6530. doi: 10.1128/mcb.14.10.6522. [DOI] [PMC free article] [PubMed] [Google Scholar]
  70. Van Aelst L., Barr M., Marcus S., Polverino A., Wigler M. Complex formation between RAS and RAF and other protein kinases. Proc Natl Acad Sci U S A. 1993 Jul 1;90(13):6213–6217. doi: 10.1073/pnas.90.13.6213. [DOI] [PMC free article] [PubMed] [Google Scholar]
  71. Vojtek A. B., Hollenberg S. M., Cooper J. A. Mammalian Ras interacts directly with the serine/threonine kinase Raf. Cell. 1993 Jul 16;74(1):205–214. doi: 10.1016/0092-8674(93)90307-c. [DOI] [PubMed] [Google Scholar]
  72. Warne P. H., Viciana P. R., Downward J. Direct interaction of Ras and the amino-terminal region of Raf-1 in vitro. Nature. 1993 Jul 22;364(6435):352–355. doi: 10.1038/364352a0. [DOI] [PubMed] [Google Scholar]
  73. Wu J., Harrison J. K., Dent P., Lynch K. R., Weber M. J., Sturgill T. W. Identification and characterization of a new mammalian mitogen-activated protein kinase kinase, MKK2. Mol Cell Biol. 1993 Aug;13(8):4539–4548. doi: 10.1128/mcb.13.8.4539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  74. Wu J., Harrison J. K., Vincent L. A., Haystead C., Haystead T. A., Michel H., Hunt D. F., Lynch K. R., Sturgill T. W. Molecular structure of a protein-tyrosine/threonine kinase activating p42 mitogen-activated protein (MAP) kinase: MAP kinase kinase. Proc Natl Acad Sci U S A. 1993 Jan 1;90(1):173–177. doi: 10.1073/pnas.90.1.173. [DOI] [PMC free article] [PubMed] [Google Scholar]
  75. Yan M., Dai T., Deak J. C., Kyriakis J. M., Zon L. I., Woodgett J. R., Templeton D. J. Activation of stress-activated protein kinase by MEKK1 phosphorylation of its activator SEK1. Nature. 1994 Dec 22;372(6508):798–800. doi: 10.1038/372798a0. [DOI] [PubMed] [Google Scholar]
  76. Yan M., Templeton D. J. Identification of 2 serine residues of MEK-1 that are differentially phosphorylated during activation by raf and MEK kinase. J Biol Chem. 1994 Jul 22;269(29):19067–19073. [PubMed] [Google Scholar]
  77. Zhang X. F., Settleman J., Kyriakis J. M., Takeuchi-Suzuki E., Elledge S. J., Marshall M. S., Bruder J. T., Rapp U. R., Avruch J. Normal and oncogenic p21ras proteins bind to the amino-terminal regulatory domain of c-Raf-1. Nature. 1993 Jul 22;364(6435):308–313. doi: 10.1038/364308a0. [DOI] [PubMed] [Google Scholar]
  78. Zheng C. F., Guan K. L. Activation of MEK family kinases requires phosphorylation of two conserved Ser/Thr residues. EMBO J. 1994 Mar 1;13(5):1123–1131. doi: 10.1002/j.1460-2075.1994.tb06361.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  79. Zheng C. F., Guan K. L. Cloning and characterization of two distinct human extracellular signal-regulated kinase activator kinases, MEK1 and MEK2. J Biol Chem. 1993 May 25;268(15):11435–11439. [PubMed] [Google Scholar]

Articles from Molecular and Cellular Biology are provided here courtesy of Taylor & Francis

RESOURCES