Published in Cell on August 12, 1988
The product of a novel growth factor activated gene, fos B, interacts with JUN proteins enhancing their DNA binding activity. EMBO J (1989) 4.27
Rapid and preferential activation of the c-jun gene during the mammalian UV response. Mol Cell Biol (1991) 3.70
Characterization of junD: a new member of the jun proto-oncogene family. EMBO J (1989) 3.55
Cross-coupling of the NF-kappa B p65 and Fos/Jun transcription factors produces potentiated biological function. EMBO J (1993) 3.28
The Epstein-Barr virus early protein EB1 activates transcription from different responsive elements including AP-1 binding sites. EMBO J (1989) 3.17
Asymmetrical recognition of the palindromic AP1 binding site (TRE) by Fos protein complexes. EMBO J (1989) 2.98
Integrating physical and genetic maps: from genomes to interaction networks. Nat Rev Genet (2007) 2.77
Autoinduction of transforming growth factor beta 1 is mediated by the AP-1 complex. Mol Cell Biol (1990) 2.73
c-rel activates but v-rel suppresses transcription from kappa B sites. Proc Natl Acad Sci U S A (1991) 2.65
Transcriptional regulation by Fos and Jun in vitro: interaction among multiple activator and regulatory domains. Mol Cell Biol (1991) 2.64
The mouse c-rel protein has an N-terminal regulatory domain and a C-terminal transcriptional transactivation domain. Mol Cell Biol (1990) 2.47
Cooperative transcriptional activity of Jun and Stat3 beta, a short form of Stat3. Proc Natl Acad Sci U S A (1995) 2.42
Isolation and characterization of fra-2, an additional member of the fos gene family. Proc Natl Acad Sci U S A (1990) 2.40
mXBP/CRE-BP2 and c-Jun form a complex which binds to the cyclic AMP, but not to the 12-O-tetradecanoylphorbol-13-acetate, response element. Mol Cell Biol (1990) 2.38
Autoregulation of fos: the dyad symmetry element as the major target of repression. EMBO J (1989) 2.37
Oncoprotein-mediated signalling cascade stimulates c-Jun activity by phosphorylation of serines 63 and 73. Mol Cell Biol (1992) 2.34
Repression of c-fos transcription is mediated through p67SRF bound to the SRE. EMBO J (1989) 2.24
Estrogen induction of the cyclin D1 promoter: involvement of a cAMP response-like element. Proc Natl Acad Sci U S A (1999) 2.19
Transcriptional activation and repression by Fos are independent functions: the C terminus represses immediate-early gene expression via CArG elements. Mol Cell Biol (1990) 2.16
Deregulated expression of human c-jun transforms primary rat embryo cells in cooperation with an activated c-Ha-ras gene and transforms rat-1a cells as a single gene. Proc Natl Acad Sci U S A (1989) 2.13
Evolutionarily conserved Ets family members display distinct DNA binding specificities. J Exp Med (1992) 2.04
Activation of endogenous c-fos proto-oncogene expression by human T-cell leukemia virus type I-encoded p40tax protein in the human T-cell line, Jurkat. J Virol (1989) 2.03
Mutual transrepression of Fos and the glucocorticoid receptor: involvement of a functional domain in Fos which is absent in FosB. EMBO J (1990) 1.97
Expression of different Jun and Fos proteins during the G0-to-G1 transition in mouse fibroblasts: in vitro and in vivo associations. Mol Cell Biol (1991) 1.91
A maize protein associated with the G-box binding complex has homology to brain regulatory proteins. Plant Cell (1992) 1.85
Trans-activation by the c-myb proto-oncogene. Nucleic Acids Res (1989) 1.84
17beta-estradiol inhibits apoptosis in MCF-7 cells, inducing bcl-2 expression via two estrogen-responsive elements present in the coding sequence. Mol Cell Biol (2000) 1.83
Mitogen-activated protein kinases mediate upregulation of hypothalamic angiotensin II type 1 receptors in heart failure rats. Hypertension (2008) 1.78
Two adjacent AP-1-like binding sites form the electrophile-responsive element of the murine glutathione S-transferase Ya subunit gene. Proc Natl Acad Sci U S A (1992) 1.77
The cellular transcription factor CREB corresponds to activating transcription factor 47 (ATF-47) and forms complexes with a group of polypeptides related to ATF-43. Mol Cell Biol (1990) 1.74
The upstream muscle-specific enhancer of the rat muscle creatine kinase gene is composed of multiple elements. Mol Cell Biol (1989) 1.73
Interference between pathway-specific transcription factors: glucocorticoids antagonize phorbol ester-induced AP-1 activity without altering AP-1 site occupation in vivo. EMBO J (1992) 1.72
Enhanced jun gene expression is an early genomic response to transforming growth factor beta stimulation. Mol Cell Biol (1989) 1.70
Osteoblasts are target cells for transformation in c-fos transgenic mice. J Cell Biol (1993) 1.70
Brain proteins in plants: an Arabidopsis homolog to neurotransmitter pathway activators is part of a DNA binding complex. Proc Natl Acad Sci U S A (1992) 1.70
Suppression of ischemia-induced fos expression and AP-1 activity by an antisense oligodeoxynucleotide to c-fos mRNA. Ann Neurol (1994) 1.69
Differential effects of the adenovirus E1A oncogene on members of the AP-1 transcription factor family. Mol Cell Biol (1990) 1.66
Interactions among LRF-1, JunB, c-Jun, and c-Fos define a regulatory program in the G1 phase of liver regeneration. Mol Cell Biol (1992) 1.64
The retinoblastoma gene product RB stimulates Sp1-mediated transcription by liberating Sp1 from a negative regulator. Mol Cell Biol (1994) 1.62
Adenovirus E4orf4 protein reduces phosphorylation of c-Fos and E1A proteins while simultaneously reducing the level of AP-1. J Virol (1992) 1.61
Destabilization of Raf-1 by geldanamycin leads to disruption of the Raf-1-MEK-mitogen-activated protein kinase signalling pathway. Mol Cell Biol (1996) 1.61
Targeted disruption of the c-fos gene demonstrates c-fos-dependent and -independent pathways for gene expression stimulated by growth factors or oncogenes. EMBO J (1994) 1.61
DNA replication origin and transcriptional enhancer in c-myc gene share the c-myc protein binding sequences. EMBO J (1989) 1.60
Phorbol esters stimulate the phosphorylation of c-Jun but not v-Jun: regulation by the N-terminal delta domain. Proc Natl Acad Sci U S A (1992) 1.60
ras-induced neuronal differentiation of PC12 cells: possible involvement of fos and jun. Mol Cell Biol (1989) 1.59
The transactivating domain of the c-Jun proto-oncoprotein is required for cotransformation of rat embryo cells. Mol Cell Biol (1991) 1.59
The Mos/MAP kinase pathway stabilizes c-Fos by phosphorylation and augments its transforming activity in NIH 3T3 cells. EMBO J (1995) 1.55
Indirect binding of human T-cell leukemia virus type I tax1 to a responsive element in the viral long terminal repeat. Mol Cell Biol (1989) 1.55
An alternative spliced form of FosB is a negative regulator of transcriptional activation and transformation by Fos proteins. Proc Natl Acad Sci U S A (1991) 1.54
Suppression of c-Jun/AP-1 activation by an inhibitor of tumor promotion in mouse fibroblast cells. Proc Natl Acad Sci U S A (1991) 1.53
A conserved C-terminal sequence that is deleted in v-ErbA is essential for the biological activities of c-ErbA (the thyroid hormone receptor). Mol Cell Biol (1993) 1.52
Interleukin-6 signals activating junB and TIS11 gene transcription in a B-cell hybridoma. Mol Cell Biol (1991) 1.49
The cis-acting phorbol ester "12-O-tetradecanoylphorbol 13-acetate"-responsive element is involved in shear stress-induced monocyte chemotactic protein 1 gene expression. Proc Natl Acad Sci U S A (1995) 1.47
A novel target cell for c-fos-induced oncogenesis: development of chondrogenic tumours in embryonic stem cell chimeras. EMBO J (1991) 1.46
The first intron of the 4F2 heavy-chain gene contains a transcriptional enhancer element that binds multiple nuclear proteins. Mol Cell Biol (1989) 1.45
An AP1-binding site in the c-fos gene can mediate induction by epidermal growth factor and 12-O-tetradecanoyl phorbol-13-acetate. Mol Cell Biol (1989) 1.45
Kid-1, a putative renal transcription factor: regulation during ontogeny and in response to ischemia and toxic injury. Mol Cell Biol (1993) 1.44
Structure-function analysis of the maf oncogene product, a member of the b-Zip protein family. J Virol (1993) 1.43
Two monomers of yeast transcription factor ADR1 bind a palindromic sequence symmetrically to activate ADH2 expression. Mol Cell Biol (1991) 1.43
Difference in transcriptional regulatory function between c-Fos and Fra-2. Nucleic Acids Res (1991) 1.43
A 36-kilodalton cellular transcription factor mediates an indirect interaction of human T-cell leukemia/lymphoma virus type I TAX1 with a responsive element in the viral long terminal repeat. Mol Cell Biol (1990) 1.42
Electrophile and antioxidant regulation of enzymes that detoxify carcinogens. Proc Natl Acad Sci U S A (1995) 1.42
Two purified factors bind to the same sequence in the enhancer of mouse MHC class I genes: one of them is a positive regulator induced upon differentiation of teratocarcinoma cells. Nucleic Acids Res (1989) 1.41
Differential DNA binding by monomeric, homodimeric, and potentially heteromeric forms of the thyroid hormone receptor. Mol Cell Biol (1991) 1.40
Molecular cloning, functional expression, and chromosomal localization of mouse hepatocyte nuclear factor 1. Proc Natl Acad Sci U S A (1990) 1.39
Molecules, cancer, and the surgeon. A review of molecular biology and its implications for surgical oncology. Ann Surg (1990) 1.39
Transcription factors AP-3 and AP-2 interact with the SV40 enhancer in a mutually exclusive manner. EMBO J (1989) 1.38
Identification of a 70-base-pair cell cycle regulatory unit within the promoter of the human thymidine kinase gene and its interaction with cellular factors. Mol Cell Biol (1991) 1.38
Sequence requirements for premature transcription arrest within the first intron of the mouse c-fos gene. Mol Cell Biol (1991) 1.36
Negative transcriptional regulation of human interleukin 2 (IL-2) gene by glucocorticoids through interference with nuclear transcription factors AP-1 and NF-AT. J Clin Invest (1993) 1.36
The cellular response to induction of the p21 c-Ha-ras oncoprotein includes stimulation of jun gene expression. EMBO J (1989) 1.35
Functional significance of an overlapping consensus binding motif for Sp1 and Zif268 in the murine adenosine deaminase gene promoter. Proc Natl Acad Sci U S A (1991) 1.31
Ras-dependent signal transduction is indispensable but not sufficient for the activation of AP1/Jun by PKC delta. EMBO J (1994) 1.30
Proteolysis by calpains: a possible contribution to degradation of p53. Mol Cell Biol (1997) 1.30
Fos and jun cooperate in transcriptional regulation via heterologous activation domains. Mol Cell Biol (1990) 1.30
Suppression of MHC class I gene expression by N-myc through enhancer inactivation. EMBO J (1989) 1.27
Induction of early-response genes KC and JE by mycobacterial lipoarabinomannans: regulation of KC expression in murine macrophages by Lsh/Ity/Bcg (candidate Nramp). Infect Immun (1994) 1.25
Lesion-induced increase in nerve growth factor mRNA is mediated by c-fos. Proc Natl Acad Sci U S A (1990) 1.24
Structure and mapping of the fosB gene. FosB downregulates the activity of the fosB promoter. Nucleic Acids Res (1992) 1.24
Unregulated expression of c-Jun or c-Fos proteins but not Jun D inhibits oestrogen receptor activity in human breast cancer derived cells. EMBO J (1991) 1.23
Epidermal growth factor stimulation of stromelysin mRNA in rat fibroblasts requires induction of proto-oncogenes c-fos and c-jun and activation of protein kinase C. Mol Cell Biol (1990) 1.22
Cis- and trans-acting elements involved in amino acid regulation of asparagine synthetase gene expression. Mol Cell Biol (1993) 1.22
Transcriptional activation by the parvoviral nonstructural protein NS-1 is mediated via a direct interaction with Sp1. Mol Cell Biol (1995) 1.20
Mitogen- and stress-activated kinase 1-mediated histone H3 phosphorylation is crucial for cell transformation. Cancer Res (2008) 1.20
Requirement of protein co-factor for the DNA-binding function of the human ski proto-oncogene product. Nucleic Acids Res (1990) 1.20
Phosphorylation of histone H3 at serine 10 is indispensable for neoplastic cell transformation. Cancer Res (2005) 1.20
Transcriptional regulation of the c-jun gene by retinoic acid and E1A during differentiation of F9 cells. EMBO J (1992) 1.20
Transactivation activity of Meq, a Marek's disease herpesvirus bZIP protein persistently expressed in latently infected transformed T cells. J Virol (1995) 1.19
Oncogenic v-Abl tyrosine kinase can inhibit or stimulate growth, depending on the cell context. EMBO J (1992) 1.18
Trans-dominant negative mutants of Fos and Jun. Proc Natl Acad Sci U S A (1990) 1.18
Mutations in the Jun delta region suggest an inverse correlation between transformation and transcriptional activation. Proc Natl Acad Sci U S A (1992) 1.15
Transcriptional activation of the cardiac myosin light chain 2 and atrial natriuretic factor genes by protein kinase C in neonatal rat ventricular myocytes. Proc Natl Acad Sci U S A (1992) 1.15
Non-leucine residues in the leucine repeats of Fos and Jun contribute to the stability and determine the specificity of dimerization. Nucleic Acids Res (1991) 1.14
Early expression of a collagenase-like hatching enzyme gene in the sea urchin embryo. EMBO J (1990) 1.13
Antisense-fos RNA causes partial reversion of the transformed phenotypes induced by the c-Ha-ras oncogene. Mol Cell Biol (1990) 1.13
Functional cooperativity between two TPA responsive elements in undifferentiated F9 embryonic stem cells. EMBO J (1990) 1.13
In vitro polyoma DNA synthesis: inhibition by 1-beta-d-arabinofuranosyl CTP. J Virol (1975) 57.17
The protein kinase family: conserved features and deduced phylogeny of the catalytic domains. Science (1988) 35.59
The protein kinase complement of the human genome. Science (2002) 35.36
Transforming gene product of Rous sarcoma virus phosphorylates tyrosine. Proc Natl Acad Sci U S A (1980) 22.30
Phorbol ester-inducible genes contain a common cis element recognized by a TPA-modulated trans-acting factor. Cell (1987) 20.61
Mammalian MAP kinase signalling cascades. Nature (2001) 18.89
Osteoprotegerin ligand is a cytokine that regulates osteoclast differentiation and activation. Cell (1998) 17.76
Oncogenic kinase signalling. Nature (2001) 16.30
JNK1: a protein kinase stimulated by UV light and Ha-Ras that binds and phosphorylates the c-Jun activation domain. Cell (1994) 16.30
Osteoprotegerin: a novel secreted protein involved in the regulation of bone density. Cell (1997) 15.96
Phosphopeptide mapping and phosphoamino acid analysis by two-dimensional separation on thin-layer cellulose plates. Methods Enzymol (1991) 15.04
Protein-tyrosine kinases. Annu Rev Biochem (1985) 14.83
Nuclear factor-kappaB: a pivotal transcription factor in chronic inflammatory diseases. N Engl J Med (1997) 14.51
Protein kinases 6. The eukaryotic protein kinase superfamily: kinase (catalytic) domain structure and classification. FASEB J (1995) 14.45
A method for isolation of intact, translationally active ribonucleic acid. DNA (1983) 13.67
OPGL is a key regulator of osteoclastogenesis, lymphocyte development and lymph-node organogenesis. Nature (1999) 12.32
Detection and quantification of phosphotyrosine in proteins. Methods Enzymol (1983) 11.89
The role of Jun, Fos and the AP-1 complex in cell-proliferation and transformation. Biochim Biophys Acta (1991) 11.78
Reversal of obesity- and diet-induced insulin resistance with salicylates or targeted disruption of Ikkbeta. Science (2001) 11.56
A cytokine-responsive IkappaB kinase that activates the transcription factor NF-kappaB. Nature (1997) 11.31
Immunosuppression by glucocorticoids: inhibition of NF-kappa B activity through induction of I kappa B synthesis. Science (1995) 11.16
Identification of an oncoprotein- and UV-responsive protein kinase that binds and potentiates the c-Jun activation domain. Genes Dev (1993) 10.01
Dissection of TNF receptor 1 effector functions: JNK activation is not linked to apoptosis while NF-kappaB activation prevents cell death. Cell (1996) 9.68
Selective activation of the JNK signaling cascade and c-Jun transcriptional activity by the small GTPases Rac and Cdc42Hs. Cell (1995) 9.30
p27, a novel inhibitor of G1 cyclin-Cdk protein kinase activity, is related to p21. Cell (1994) 8.90
The IkappaB kinase complex (IKK) contains two kinase subunits, IKKalpha and IKKbeta, necessary for IkappaB phosphorylation and NF-kappaB activation. Cell (1997) 8.74
Platelet-derived growth factor induces rapid but transient expression of the c-fos gene and protein. Nature (1985) 8.36
Integrin-mediated signal transduction linked to Ras pathway by GRB2 binding to focal adhesion kinase. Nature (1995) 8.25
Activated T cells regulate bone loss and joint destruction in adjuvant arthritis through osteoprotegerin ligand. Nature (1999) 8.23
Isolation of a human cyclin cDNA: evidence for cyclin mRNA and protein regulation in the cell cycle and for interaction with p34cdc2. Cell (1989) 8.19
The regulation of transcription by phosphorylation. Cell (1992) 7.99
osteoprotegerin-deficient mice develop early onset osteoporosis and arterial calcification. Genes Dev (1998) 7.81
AU binding proteins recruit the exosome to degrade ARE-containing mRNAs. Cell (2001) 7.79
The jun proto-oncogene is positively autoregulated by its product, Jun/AP-1. Cell (1988) 7.76
Transcription factor AP-2 mediates induction by two different signal-transduction pathways: protein kinase C and cAMP. Cell (1987) 7.75
Protein kinase B/Akt-mediated phosphorylation promotes nuclear exclusion of the winged helix transcription factor FKHR1. Proc Natl Acad Sci U S A (1999) 7.70
Activation by IKKalpha of a second, evolutionary conserved, NF-kappa B signaling pathway. Science (2001) 7.66
A thousand and one protein kinases. Cell (1987) 7.61
The tyrosine kinase negative regulator c-Cbl as a RING-type, E2-dependent ubiquitin-protein ligase. Science (1999) 7.60
Characterization of DNA sequences through which cadmium and glucocorticoid hormones induce human metallothionein-IIA gene. Nature (1984) 7.57
Oncogene jun encodes a sequence-specific trans-activator similar to AP-1. Nature (1988) 7.45
Human cyclin A is adenovirus E1A-associated protein p60 and behaves differently from cyclin B. Nature (1990) 7.34
Human cyclins A and B1 are differentially located in the cell and undergo cell cycle-dependent nuclear transport. J Cell Biol (1991) 7.18
Human metallothionein genes--primary structure of the metallothionein-II gene and a related processed gene. Nature (1982) 7.05
An activity phosphorylating tyrosine in polyoma T antigen immunoprecipitates. Cell (1979) 7.02
TRAF6 deficiency results in osteopetrosis and defective interleukin-1, CD40, and LPS signaling. Genes Dev (1999) 6.93
Activation of protein kinase C decreases phosphorylation of c-Jun at sites that negatively regulate its DNA-binding activity. Cell (1991) 6.89
Phospholipase C-gamma is a substrate for the PDGF and EGF receptor protein-tyrosine kinases in vivo and in vitro. Cell (1989) 6.88
Transcriptional interference between c-Jun and the glucocorticoid receptor: mutual inhibition of DNA binding due to direct protein-protein interaction. Cell (1990) 6.84
Activation of transcription by two factors that bind promoter and enhancer sequences of the human metallothionein gene and SV40. Nature (1987) 6.76
Evidence that the phosphorylation of tyrosine is essential for cellular transformation by Rous sarcoma virus. Cell (1980) 6.76
Signal transduction by tumor necrosis factor and its relatives. Trends Cell Biol (2001) 6.73
Characterization of Rous sarcoma virus src gene products synthesized in vitro. J Virol (1978) 6.39
IKK-gamma is an essential regulatory subunit of the IkappaB kinase complex. Nature (1998) 6.15
Differential activation of ERK and JNK mitogen-activated protein kinases by Raf-1 and MEKK. Science (1994) 6.07
AP-1 in cell proliferation and survival. Oncogene (2001) 6.07
Positive and negative regulation of IkappaB kinase activity through IKKbeta subunit phosphorylation. Science (1999) 5.95
The IKKbeta subunit of IkappaB kinase (IKK) is essential for nuclear factor kappaB activation and prevention of apoptosis. J Exp Med (1999) 5.79
Tumor necrosis factor receptor family member RANK mediates osteoclast differentiation and activation induced by osteoprotegerin ligand. Proc Natl Acad Sci U S A (1999) 5.78
Vinculin: a cytoskeletal target of the transforming protein of Rous sarcoma virus. Cell (1981) 5.74
Changes in protein phosphorylation in Rous sarcoma virus-transformed chicken embryo cells. Mol Cell Biol (1981) 5.67
Activation of cAMP and mitogen responsive genes relies on a common nuclear factor. Nature (1994) 5.65
Comparison of the expression of the src gene of Rous sarcoma virus in vitro and in vivo. J Virol (1978) 5.30
Multiple Ras functions can contribute to mammalian cell transformation. Cell (1995) 5.24
Receptor protein-tyrosine kinases and their signal transduction pathways. Annu Rev Cell Biol (1994) 5.24
Abnormal morphogenesis but intact IKK activation in mice lacking the IKKalpha subunit of IkappaB kinase. Science (1999) 5.15
Epidermal growth factor induces rapid tyrosine phosphorylation of proteins in A431 human tumor cells. Cell (1981) 5.08
Inhibition of JNK activation through NF-kappaB target genes. Nature (2001) 5.03
Tyr527 is phosphorylated in pp60c-src: implications for regulation. Science (1986) 4.99
Receptor-mediated endocytosis of transferrin in developmentally totipotent mouse teratocarcinoma stem cells. J Biol Chem (1981) 4.86
p53-dependent apoptosis in the absence of transcriptional activation of p53-target genes. Nature (1994) 4.77
Identification of a dual specificity kinase that activates the Jun kinases and p38-Mpk2. Science (1995) 4.74
Oncogenic and transcriptional cooperation with Ha-Ras requires phosphorylation of c-Jun on serines 63 and 73. Nature (1991) 4.74
Prevention of fat-induced insulin resistance by salicylate. J Clin Invest (2001) 4.74
Anti-inflammatory cyclopentenone prostaglandins are direct inhibitors of IkappaB kinase. Nature (2000) 4.66
A human peptidyl-prolyl isomerase essential for regulation of mitosis. Nature (1996) 4.65
Human eukaryotic translation initiation factor 4G (eIF4G) recruits mnk1 to phosphorylate eIF4E. EMBO J (1999) 4.65
A structural basis for substrate specificities of protein Ser/Thr kinases: primary sequence preference of casein kinases I and II, NIMA, phosphorylase kinase, calmodulin-dependent kinase II, CDK5, and Erk1. Mol Cell Biol (1996) 4.61
Mapping of the inducible IkappaB phosphorylation sites that signal its ubiquitination and degradation. Mol Cell Biol (1996) 4.56
The osteoclast differentiation factor osteoprotegerin-ligand is essential for mammary gland development. Cell (2000) 4.53
JNK2 contains a specificity-determining region responsible for efficient c-Jun binding and phosphorylation. Genes Dev (1994) 4.50
Prolonged activation of jun and collagenase genes by tumour necrosis factor-alpha. Nature (1989) 4.42
MNK1, a new MAP kinase-activated protein kinase, isolated by a novel expression screening method for identifying protein kinase substrates. EMBO J (1997) 4.39
JNK is involved in signal integration during costimulation of T lymphocytes. Cell (1994) 4.36
Protein kinase C phosphorylation of the EGF receptor at a threonine residue close to the cytoplasmic face of the plasma membrane. Nature (1984) 4.27
Structural basis for phosphoserine-proline recognition by group IV WW domains. Nat Struct Biol (2000) 4.25
Structural and functional analysis of the mitotic rotamase Pin1 suggests substrate recognition is phosphorylation dependent. Cell (1997) 4.24
Phosphorylation sites in enolase and lactate dehydrogenase utilized by tyrosine protein kinases in vivo and in vitro. J Biol Chem (1984) 4.20
Jun-B differs in its biological properties from, and is a negative regulator of, c-Jun. Cell (1989) 4.17
Ha-Ras augments c-Jun activity and stimulates phosphorylation of its activation domain. Nature (1991) 4.17