Activating Transcription Factor-2 Regulates Phosphoenolpyruvate Carboxykinase Transcription through a Stress-inducible Mitogen-activated Protein Kinase Pathway

Several protein-nucleic acid complexes are observed when nuclear extracts from hepatoma cells are assayed for binding to the cAMP response element found in the phosphoenolpyruvate carboxykinase-cytosolic (PEPCK-C) promoter. Although cAMP response element-binding protein and CCAAT/enhancer binding proteins α and β have been identified as liver factors that bind this motif, an uncharacterized, slower migrating complex was also observed. We identify activating transcription factor-2 (ATF-2) as the factor in this complex and show that ATF-2 stimulates expression from the PEPCK-C promoter. ATF-2 is a basic-leucine zipper transcription factor and a target for stress-activated protein kinases. We demonstrate that p38β mitogen-activated protein (MAP) kinase augments ATF-2 transactivation activity on the PEPCK-C promoter, which is consistent with the interpretation that PEPCK-C promoter activity is maintained under stress through a p38 MAP kinase dependent pathway. In this regard, we show that treatment with sodium arsenite, a known activator of p38 MAP kinases, also stimulates expression from the PEPCK promoter. These results show that ATF-2 can stimulate transcription of the PEPCK-C promoter and support a role for stress inducible kinases in the maintenance of PEPCK-C expression. Several protein-nucleic acid complexes are observed when nuclear extracts from hepatoma cells are assayed for binding to the cAMP response element found in the phosphoenolpyruvate carboxykinase-cytosolic (PEPCK-C) promoter. Although cAMP response element-binding protein and CCAAT/enhancer binding proteins α and β have been identified as liver factors that bind this motif, an uncharacterized, slower migrating complex was also observed. We identify activating transcription factor-2 (ATF-2) as the factor in this complex and show that ATF-2 stimulates expression from the PEPCK-C promoter. ATF-2 is a basic-leucine zipper transcription factor and a target for stress-activated protein kinases. We demonstrate that p38β mitogen-activated protein (MAP) kinase augments ATF-2 transactivation activity on the PEPCK-C promoter, which is consistent with the interpretation that PEPCK-C promoter activity is maintained under stress through a p38 MAP kinase dependent pathway. In this regard, we show that treatment with sodium arsenite, a known activator of p38 MAP kinases, also stimulates expression from the PEPCK promoter. These results show that ATF-2 can stimulate transcription of the PEPCK-C promoter and support a role for stress inducible kinases in the maintenance of PEPCK-C expression. The enzyme phosphoenolpyruvate carboxykinase-cytosolic (PEPCK-C) 1The abbreviations used are: PEPCK-Cphosphoenolpyruvate carboxykinase-cytosolicC/EBPCCAAT/enhancer-binding proteinCREBcAMP response element-binding proteinCREMcAMP-responsive element modulatorATF-2activating transcription factor-2CRE-1cAMP response element-1JNKc-Jun N-terminal kinaseMAP kinasemitogen-activated protein kinasePKAprotein kinase A. catalyzes a regulatory step in gluconeogenesis and is regulated primarily at the level of transcription initiation (1Nizielski S.E. Arizmendi C. Shteyngarts A.R. Farrell C.J. Friedman J.E. Am. J. Physiol. 1996; 270: R1005-R1012PubMed Google Scholar, 2Hanson R.W. Reshef L. Annu. Rev. Biochem. 1997; 66: 581-611Crossref PubMed Scopus (634) Google Scholar). The PEPCK-C promoter is a model for metabolic regulation of gene expression. It is expressed primarily in liver, kidney, small intestine, and adipose tissue, where it integrates cues arising from diverse signaling pathways. For example, PEPCK-C transcription in liver is induced by the action of glucagon, thyroid hormone, and glucocorticoids (3Tilghman S.M. Hanson R.W. Reshef L. Hopgood M.F. Ballard F.J. Proc. Natl. Acad. Sci. U. S. A. 1974; 71: 1304-1308Crossref PubMed Scopus (83) Google Scholar, 4Loose D.S. Cameron D.K. Short H.P. Hanson R.W. Biochemistry. 1985; 24: 4509-4512Crossref PubMed Scopus (62) Google Scholar, 5Gunn J.M. Hanson R.W. Meyuhas O. Reshef L. Ballard F.J. Biochem. J. 1975; 150: 195-203Crossref PubMed Scopus (59) Google Scholar); whereas the action of a single hormone, insulin, exerts dominant negative control (6Kioussis D. Reshef L. Cohen H. Tilghman S.M. Iynedjian P.B. Ballard F.J. Hanson R.W. J. Biol. Chem. 1978; 253: 4327-4332Abstract Full Text PDF PubMed Google Scholar). PEPCK-C transcription also responds to nutritional status, where starvation signals act inductively and a carbohydrate-rich meal results in repression (3Tilghman S.M. Hanson R.W. Reshef L. Hopgood M.F. Ballard F.J. Proc. Natl. Acad. Sci. U. S. A. 1974; 71: 1304-1308Crossref PubMed Scopus (83) Google Scholar). phosphoenolpyruvate carboxykinase-cytosolic CCAAT/enhancer-binding protein cAMP response element-binding protein cAMP-responsive element modulator activating transcription factor-2 cAMP response element-1 c-Jun N-terminal kinase mitogen-activated protein kinase protein kinase A. The minimal sequence of the PEPCK-C promoter sufficient for reduplication of hormonal regulation in liver has been mapped to the region encompassing −460 to +73 (7McGrane M.M. de Vente J. Yun J. Bloom J. Park E. Wynshaw-Boris A. Wagner T. Rottman F.M. Hanson R.W. J. Biol. Chem. 1988; 263: 11443-11451Abstract Full Text PDF PubMed Google Scholar, 8McGrane M.M. Yun J.S. Moorman A.F. Lamers W.H. Hendrick G.K. Arafah B.M. Park E.A. Wagner T.E. Hanson R.W. J. Biol. Chem. 1990; 265: 22371-22379Abstract Full Text PDF PubMed Google Scholar, 9Short M.K. Clouthier D.E. Schaefer I.M. Hammer R.E. Magnuson M.A. Beale E.G. Mol. Cell. Biol. 1992; 12: 1007-1020Crossref PubMed Scopus (101) Google Scholar, 10Eisenberger C.L. Nechushtan H. Cohen H. Shani M. Reshef L. Mol. Cell. Biol. 1992; 12: 1396-1403Crossref PubMed Scopus (48) Google Scholar), and many of the transcription factors that bind elements in this region have been identified (2Hanson R.W. Reshef L. Annu. Rev. Biochem. 1997; 66: 581-611Crossref PubMed Scopus (634) Google Scholar, 11Nizielski S.E. Lechner P.S. Croniger C.M. Wang N.D. Darlington G.J. Hanson R.W. J. Nutr. 1996; 126: 2697-2708PubMed Google Scholar). For example, glucagon secretion leads to an increase in cAMP levels, which exerts effects by inducing factors that bind to the element denoted cyclic AMP response element I (CRE-1) and may also induce factors that bind to the element denoted P3. Prima facie, CREB might be anticipated as the primary factor impacted by increased cAMP levels. However, PEPCK-C expression was reported to be normal in CREB knockout mice (12Hummler E. Cole T.J. Blendy J.A. Ganss R. Aguzzi A. Schmid W. Beermann F. Schutz G. Proc. Natl. Acad. Sci. U. S. A. 1994; 91: 5647-5651Crossref PubMed Scopus (335) Google Scholar). Binding to CRE-1 has also been reported for C/EBPα (13Park E.A. Roesler W.J. Liu J. Klemm D.J. Gurney A.L. Thatcher J.D. Shuman J. Friedman A. Hanson R.W. Mol. Cell. Biol. 1990; 10: 6264-6272Crossref PubMed Scopus (174) Google Scholar), C/EBPβ (14Park E.A. Gurney A.L. Nizielski S.E. Hakimi P. Cao Z. Moorman A. Hanson R.W. J. Biol. Chem. 1993; 268: 613-619Abstract Full Text PDF PubMed Google Scholar), AP1 (15Gurney A.L. Park E.A. Giralt M. Liu J. Hanson R.W. J. Biol. Chem. 1992; 267: 18133-18139Abstract Full Text PDF PubMed Google Scholar), and D-site binding protein (16Roesler W.J. McFie P.J. Dauvin C. J. Biol. Chem. 1992; 267: 21235-21243Abstract Full Text PDF PubMed Google Scholar). In fact, evidence from gene deletion experiments supports a role for C/EBPs α and β in the regulation of PEPCK-C expression (17Wang N.D. Finegold M.J. Bradley A. Ou C.N. Abdelsayed S.V. Wilde M.D. Taylor L.R. Wilson D.R. Darlington G.J. Science. 1995; 269: 1108-1112Crossref PubMed Scopus (838) Google Scholar). The PEPCK-C gene is essential in humans (18Vidnes J. Sovik O. Acta. Paediatr. Scand. 1976; 65: 297-305Crossref PubMed Scopus (13) Google Scholar), and its expression is not only maintained but, in fact, induced following partial hepatectomy (19Diehl A.M. Yang S.Q. Yin M. Lin H.Z. Nelson S. Bagby G. Hepatology. 1995; 22: 252-261PubMed Google Scholar). We uncovered the PEPCK-C CRE-1 motif TTAC GTCAduring a search of promoter sequences as a perfect match to the consensus reported for ATF-2 homodimers (20Benbrook D.M. Jones N.C. Nucleic Acids Res. 1994; 22: 1463-1469Crossref PubMed Scopus (135) Google Scholar). ATF-2, a basic-leucine zipper transcription factor, is expressed in liver tissue (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar) and exhibits increased DNA binding and transcriptional activation activities following phosphorylation of specific residues by p38 MAP kinases (22Raingeaud J. Gupta S. Rogers J.S. Dickens M. Han J. Ulevitch R.J. Davis R.J. J. Biol. Chem. 1995; 270: 7420-7426Abstract Full Text Full Text PDF PubMed Scopus (2046) Google Scholar) or c-Jun N-terminal MAP kinases (JNK) (23Livingstone C. Patel G. Jones N. EMBO J. 1995; 14: 1785-1797Crossref PubMed Scopus (476) Google Scholar, 24van Dam H. Wilhelm D. Herr I. Steffen A. Herrlich P. Angel P. EMBO J. 1995; 14: 1798-1811Crossref PubMed Scopus (571) Google Scholar). Because PEPCK-C transcription increases after partial hepatectomy (19Diehl A.M. Yang S.Q. Yin M. Lin H.Z. Nelson S. Bagby G. Hepatology. 1995; 22: 252-261PubMed Google Scholar), a stress condition, we considered that ATF-2 may contribute to regulation through the CRE-1 element. We show here that ATF-2 binds the PEPCK-C CRE-1 element, that sense ATF-2 expression correlates with increased promoter activity, and that antisense ATF-2 expression correlates with decreased promoter activity. Furthermore, expression of p38β MAP kinase, a known modifier of ATF-2, correlates with increased reporter activity, while cotransfection of p38β MAP kinase and ATF-2 shows augmented transcriptional activation. These results support a role for ATF-2 in the maintenance of PEPCK-C expression in the liver that may have special relevance under stress conditions. Fao cells are a hepatoma derivative that exhibit many of the characteristics of differentiated hepatocytes and were kindly provided by Dr. Mary Weiss (Institut Pasteur) (25Deschatrette J. Weiss M.C. Biochimie ( Paris ). 1974; 56: 1603-1611Crossref PubMed Scopus (300) Google Scholar). Fao cells were maintained in Coon's modified, Ham's F-12 medium (Life Technologies, Inc.) supplemented with 5% fetal calf serum, penicillin, streptomycin, and glutamine. The ATF-2 expression plasmid has been described (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar). The human p38β expression plasmid was provided by Jiahuai Han (The Scripps Research Institute) (26Jiang Y. Chen C. Li Z. Guo W. Gegner J.A. Lin S. Han J. J. Biol. Chem. 1996; 271: 17920-17926Abstract Full Text Full Text PDF PubMed Scopus (660) Google Scholar). The Reporter plasmid PEPCK −275 was prepared by polymerase chain reaction of rat genomic DNA using 5′ primer GGTACC ACA GTC AGCG GTC AAA GTT TAG TCA ATC and 3′ primer GCTCGA GAG ATC TCA GAG CGT CTC GCC GG, which encompasses positions −275 through +73 of the PEPCK-C promoter using numbering according to Roesler et al. (27Roesler W.J. Vandenbark G.R. Hanson R.W. J. Biol. Chem. 1989; 264: 9657-9664Abstract Full Text PDF PubMed Google Scholar). For sodium arsenite treatment, 1 × 106 Fao cells were plated on a 10-cm dish, transfected by standard calcium phosphate treatment, washed, and fed complete medium for 48 h. Medium was supplemented with 50 μm sodium arsenite (Sigma) for 6 h prior to cell harvest. Full-length C/EBPα and ATF-2 proteins were prepared by in vitro transcription-coupled translation (TNT, Promega, Madison, WI.) under conditions described by the manufacturer. A double-stranded oligonucleotide encoding the PEPCK-C CRE-1 sequence (promoter positions −99 to −76) was used for gel shift analysis: 5′ CCGGCCCC TTACGTCA GAGGCG. Binding reactions were assembled without probe and held 5 min on ice followed by 5 min at room temperature. Probe was added with further room temperature incubation for 30 min. Samples were separated in 4% acrylamide, 0.5× TBE (0.045m Tris, 0.045 m boric acid, 1.0 mmEDTA (pH 8.0) gels run at 200 V constant voltage (28Sambrook J. Fritsch E.F. Maniatis T. Molecular Cloning: A Laboratory Manual. 2nd Ed. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY1989: 6.7-16.33Google Scholar). Fao cells were transfected by the standard calcium phosphate method (28Sambrook J. Fritsch E.F. Maniatis T. Molecular Cloning: A Laboratory Manual. 2nd Ed. Cold Spring Harbor Laboratory, Cold Spring Harbor, NY1989: 6.7-16.33Google Scholar). Cells were incubated with DNA precipitates for 16 h, washed, and maintained in complete medium 48 h prior to harvest. Relative luciferase and β-galactosidase activities were determined as described (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar). Basal promoter activity is reported as the activity observed after transfection of the reporter plus an appropriate amount of empty expression vector. In all cases, transfection data represent the mean of three independent experiments, where error bars indicate the S.D. of the mean. Fao cells were harvested in Nonidet P-40 lysis buffer, and 30–50 μg of nuclear protein was fractionated by SDS-polyacrylamide gel electrophoresis. Proteins were electroblotted to Immobilon-P (Millipore), and membranes were blocked in TBS, 0.02% Tween 20 containing 5% non-fat milk. Primary antibody (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar) was followed with goat anti-rabbit-conjugated horseradish peroxidase (Amersham Pharmacia Biotech) and detected by enhanced chemiluminescence using ECL reagent (Amersham Pharmacia Biotech) as described (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar). The transcription factors CREB (29Quinn P.G. Wong T.W. Magnuson M.A. Shabb J.B. Granner D.K. Mol. Cell. Biol. 1988; 8: 3467-3475Crossref PubMed Scopus (125) Google Scholar), C/EBPα (13Park E.A. Roesler W.J. Liu J. Klemm D.J. Gurney A.L. Thatcher J.D. Shuman J. Friedman A. Hanson R.W. Mol. Cell. Biol. 1990; 10: 6264-6272Crossref PubMed Scopus (174) Google Scholar), C/EBPβ (14Park E.A. Gurney A.L. Nizielski S.E. Hakimi P. Cao Z. Moorman A. Hanson R.W. J. Biol. Chem. 1993; 268: 613-619Abstract Full Text PDF PubMed Google Scholar), AP1 (15Gurney A.L. Park E.A. Giralt M. Liu J. Hanson R.W. J. Biol. Chem. 1992; 267: 18133-18139Abstract Full Text PDF PubMed Google Scholar), andD-site-binding protein (16Roesler W.J. McFie P.J. Dauvin C. J. Biol. Chem. 1992; 267: 21235-21243Abstract Full Text PDF PubMed Google Scholar) have been reported to bind the PEPCK-C CRE-1 element (Fig.1 A) (13Park E.A. Roesler W.J. Liu J. Klemm D.J. Gurney A.L. Thatcher J.D. Shuman J. Friedman A. Hanson R.W. Mol. Cell. Biol. 1990; 10: 6264-6272Crossref PubMed Scopus (174) Google Scholar). Notably, the CRE-1 site matches the consensus sequence reported for ATF-2 homodimers (Fig.1 A) (20Benbrook D.M. Jones N.C. Nucleic Acids Res. 1994; 22: 1463-1469Crossref PubMed Scopus (135) Google Scholar) rather than the CREB or AP1 consensus sequences. Because ATF-2 expression was recently demonstrated in rat liver (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar), we wondered if it bound the CRE-1 site. As shown in Fig. 1 B, the slowest migrating shift produced with hepatoma nuclear extracts (lane 1) is supershifted when anti-ATF-2 serum is included in the binding reaction (lane 3). By comparison, C/EBPα, a factor reported to bind this site, also produces a supershift complex (lane 2) of specific However, the C/EBPα supershift complex is not and the from which the supershift complex is not demonstrate the positions for protein-nucleic acid shift reactions were with C/EBPα and ATF-2 prepared vitro transcription-coupled translation and These results demonstrate that ATF-2, C/EBPα, binds the CRE-1 element in the PEPCK-C promoter. if ATF-2 might have on PEPCK-C promoter activity, we transfected Fao hepatoma cells with a luciferase reporter encompassing −275 to +73 of the PEPCK promoter 1 A) (27Roesler W.J. Vandenbark G.R. Hanson R.W. J. Biol. Chem. 1989; 264: 9657-9664Abstract Full Text PDF PubMed Google Scholar). region the CRE-1 motif as as the motif, reported binding for As shown in Fig. luciferase activity increased to with of transfected sense ATF-2 expression we the reporter with of antisense ATF-2 expression As shown in Fig. B, reporter activity decreased when cells were with plasmid encoding antisense The shows nuclear extracts from a transfection and that ATF-2 protein antisense ATF-2 expression (lane 2) and increase sense ATF-2 expression (lane to ATF-2 (lane These results are consistent with a role for ATF-2 in the regulation of PEPCK-C gene expression. ATF-2 is a known for p38 MAP kinases (26Jiang Y. Chen C. Li Z. Guo W. Gegner J.A. Lin S. Han J. J. Biol. Chem. 1996; 271: 17920-17926Abstract Full Text Full Text PDF PubMed Scopus (660) Google Scholar), a of stress-activated protein kinases in the MAP kinase J. J.D. L. Ulevitch R.J. Science. 1994; 265: PubMed Scopus Google Scholar, S. D. D. M.J. et 1994; PubMed Scopus Google Scholar, J. Cohen P. S. M. A. D. T. A.R. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar, L. F. Jones E. S. J. J. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar). we the of p38β expression on a reporter containing the minimal kinase promoter by of ATF-2 consensus (21Shuman J.D. Cheong J. Coligan J.E. J. Biol. Chem. 1997; 272: 12793-12800Abstract Full Text Full Text PDF PubMed Scopus (79) Google Scholar). As shown in p38β MAP kinase expression with an increase in reporter activity. is with expression of ATF-2 which stimulates activity ATF-2 and p38β MAP kinase are reporter activity increased In expression of a transfected p38β MAP kinase activity that was with not These results that p38β MAP kinase augments ATF-2 activity in Fao hepatoma We the PEPCK −275 which shows of transcription the that were in the of complete medium and conditions for PEPCK-C expression. As shown in Fig. B, p38β MAP kinase stimulates transcription is with the observed expression of ATF-2 ATF-2 and p38β MAP kinase stimulate PEPCK −275 reporter activity These results are to using the minimal show of transcriptional activation. is to factors that contribute to regulation of the PEPCK-C promoter. the level of the results are consistent with the that ATF-2 in maintenance of PEPCK-C conditions that a MAP kinase As a control for the effects we observed with p38β MAP kinase, we protein kinase A or with As shown in Fig. expression of protein kinase A reporter activity is not as PEPCK-C is a known target for cAMP ATF-2 was with activity was which is to ATF-2 results were with which shows activity that is to ATF-2 is reporter activity increases to ATF-2 These that the transcriptional we observed with ATF-2 and p38β MAP kinase is not to protein kinase, is to stress protein kinases. Because sodium arsenite p38 MAP kinases J. Cohen P. S. M. A. D. T. A.R. Cell. 1994; Full Text PDF PubMed Scopus Google Scholar), a we in Fao cells using specific for p38 MAP kinase not we wondered if PEPCK-C promoter activity be As a Fao cells transfected with the PEPCK −275 reporter gene were 48 h in complete medium followed by treatment with 50 μm sodium arsenite for 6 h. As shown in promoter activity after arsenite treatment was with that observed following transfection of However, when ATF-2 were to treatment with sodium arsenite, a increase in luciferase activity was observed. transcriptional effects observed after arsenite treatment were blocked in cells transfected with an antisense ATF-2 expression These results are consistent with the interpretation that which the p38 MAP kinase contribute to maintenance of PEPCK-C The CRE-1 site and of the PEPCK-C promoter is a perfect match to the consensus binding sequence reported for ATF-2 homodimers (20Benbrook D.M. Jones N.C. Nucleic Acids Res. 1994; 22: 1463-1469Crossref PubMed Scopus (135) Google Scholar) and ATF-2 is of the transcription factors in hepatoma cell nuclear extracts that binds this sequence in shift with sense and antisense ATF-2 increase and reporter gene activity by the PEPCK-C promoter. is to as PEPCK-C catalyzes a step of the pathway. reaction is a that is maintained for example, PEPCK-C increased following of the liver (19Diehl A.M. Yang S.Q. Yin M. Lin H.Z. Nelson S. Bagby G. Hepatology. 1995; 22: 252-261PubMed Google Scholar). a that stress induced by sodium arsenite PEPCK-C expression in hepatoma cells C. Granner D.K. 1997; PubMed Scopus Google Scholar), are consistent with a for ATF-2 in PEPCK-C expression stress conditions. Because of of it is to the be that the of PEPCK-C expression from conditions that are whereas from conditions that promoter activity to levels. ATF-2 is expressed in is a for MAP kinases the p38 and the stress-activated and exhibits increased transcription activating and DNA binding activities in the (23Livingstone C. Patel G. Jones N. EMBO J. 1995; 14: 1785-1797Crossref PubMed Scopus (476) Google Scholar, 24van Dam H. Wilhelm D. Herr I. Steffen A. Herrlich P. Angel P. EMBO J. 1995; 14: 1798-1811Crossref PubMed Scopus (571) Google Scholar). The p38 MAP kinases and the the residues in ATF-2, and A. Cohen P. M. EMBO J. 1997; PubMed Scopus Google Scholar). Although the here were to p38 MAP kinases, we that MAP kinases in a of from conditions that are for PEPCK-C activity, serum and we observed of PEPCK-C promoter activity by transfection of ATF-2 or p38β MAP kinase ATF-2 and p38β MAP kinase were augmented transcriptional activation was observed. to augmented transcription with and ATF-2 or with and ATF-2 that the transcriptional increase was In treatment of Fao cells the of with sodium arsenite, an activator of p38 MAP kinases, in a increase promoter activity. The that this was expression of antisense ATF-2 These results support a role for ATF-2 in the maintenance of PEPCK-C expression in hepatocytes in response to signals that MAP kinases. are consistent with results from gene deletion deletion of the encoding transcription factors and protein show in (2Hanson R.W. Reshef L. Annu. Rev. Biochem. 1997; 66: 581-611Crossref PubMed Scopus (634) Google Scholar). In deletion of the gene for C/EBPα results in to liver to tissue, and (17Wang N.D. Finegold M.J. Bradley A. Ou C.N. Abdelsayed S.V. Wilde M.D. Taylor L.R. Wilson D.R. Darlington G.J. Science. 1995; 269: 1108-1112Crossref PubMed Scopus (838) Google Scholar). However, C/EBPα is an protein T. J. J. Biol. Chem. 1992; 267: Full Text PDF PubMed Google Scholar), expression increase following partial hepatectomy (19Diehl A.M. Yang S.Q. Yin M. Lin H.Z. Nelson S. Bagby G. Hepatology. 1995; 22: 252-261PubMed Google Scholar). In fact, C/EBPα under of consistent with its effects in cell D. Mol. Cell. Biol. 1992; 12: PubMed Google Scholar, Friedman Science. PubMed Scopus Google Scholar, T.J. Science. 1992; PubMed Scopus Google Scholar). Although C/EBPβ expression increases after partial hepatectomy (19Diehl A.M. Yang S.Q. Yin M. Lin H.Z. Nelson S. Bagby G. Hepatology. 1995; 22: 252-261PubMed Google Scholar), it is not a known for MAP kinases, that proteins and proteins are not of PEPCK-C expression conditions of Although transcriptional effects observed in cell not regulation as it in (2Hanson R.W. Reshef L. Annu. Rev. Biochem. 1997; 66: 581-611Crossref PubMed Scopus (634) Google Scholar), support a role for ATF-2 as a of the PEPCK-C promoter conditions of We Dr. Han (The Scripps Research Institute) for p38β and p38β kinase expression Dr. for expression and Dr. for expression We are to Dr. Mary Weiss of the for the Fao cell We for with We and for on the