Despite Increased ATF4 Binding at the C/EBP-ATF Composite Site following Activation of the Unfolded Protein Response, System A Transporter 2 (SNAT2) Transcription Activity Is Repressed in HepG2 Cells

Abstract

The activated amino acid response (AAR) and unfolded protein response (UPR) stress signaling pathways converge at the phosphorylation of translation initiation factor eIF2α. This eIF2α modification suppresses global protein synthesis but enhances translation of selected mRNAs such as that for activating transcription factor 4 (ATF4). An ATF4 target gene, SNAT2 (system A sodium-dependent neutral amino acid transporter 2), contains a C/EBP-ATF site that binds ATF4 and triggers increased transcription during the AAR. However, the present studies show that despite increased ATF4 binding to the SNAT2 gene during UPR activation in HepG2 human hepatoma cells, transcription activity was not enhanced. Hyperacetylation of histone H3 and recruitment of the general transcription factors at the HepG2 SNAT2 promoter occurred in response to the AAR but not the UPR. In contrast, the UPR did enhance transcription from a plasmid-based reporter gene driven by a SNAT2 genomic fragment containing the C/EBP-ATF site. Simultaneous activation of the AAR and the UPR pathways revealed that the UPR actually suppressed the increased SNAT2 transcription by the AAR pathway, demonstrating that the UPR pathway generates a repressive signal that acts downstream of ATF4 binding. The activated amino acid response (AAR) and unfolded protein response (UPR) stress signaling pathways converge at the phosphorylation of translation initiation factor eIF2α. This eIF2α modification suppresses global protein synthesis but enhances translation of selected mRNAs such as that for activating transcription factor 4 (ATF4). An ATF4 target gene, SNAT2 (system A sodium-dependent neutral amino acid transporter 2), contains a C/EBP-ATF site that binds ATF4 and triggers increased transcription during the AAR. However, the present studies show that despite increased ATF4 binding to the SNAT2 gene during UPR activation in HepG2 human hepatoma cells, transcription activity was not enhanced. Hyperacetylation of histone H3 and recruitment of the general transcription factors at the HepG2 SNAT2 promoter occurred in response to the AAR but not the UPR. In contrast, the UPR did enhance transcription from a plasmid-based reporter gene driven by a SNAT2 genomic fragment containing the C/EBP-ATF site. Simultaneous activation of the AAR and the UPR pathways revealed that the UPR actually suppressed the increased SNAT2 transcription by the AAR pathway, demonstrating that the UPR pathway generates a repressive signal that acts downstream of ATF4 binding. A wide variety of stress signals activate one or more of a set of eukaryotic initiation factor 2α (eIF2α) 2The abbreviations used are: eIF2α, eukaryotic initiation factor 2α; ATF4, activating transcription factor 4; AAR, amino acid response; AARE, amino acid-response element; ASNS, asparagine synthetase; BiP/GRP78, immunoglobulin heavy chain-binding protein/glucose-regulated protein 78; C/EBP, CCAAT/enhancer-binding protein; ChIP, chromatin immunoprecipitation; CHOP, C/EBP homology protein; ERSE, endoplasmic reticulum stress element; GAPDH, glyceraldehyde-3-phosphate dehydrogenase gene; GCN2, general control nonderepressible; HisOH, histidinol; LAP, liver-enriched activating protein; NSRE, nutrient sensing response element; PERK, double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase; qRT, quantitative real time; RT, reverse transcriptase; SNAT2, system A sodium-dependent neutral amino acid transporter 2; TBP, TATA-binding protein; TFII, general transcription factor; Tg, thapsigargin; UPR, unfolded protein response; XBP1, X-box binding protein 1; MEM, minimal essential medium; nt, nucleotide; siRNA, short interfering RNA; pol, polymerase; GTF, general transcription factor; hnRNA, heterogeneous nuclear RNA; bZIP, basic leucine zipper; ER, endoplasmic reticulum; CREB, cAMP-response-element-binding protein. 2The abbreviations used are: eIF2α, eukaryotic initiation factor 2α; ATF4, activating transcription factor 4; AAR, amino acid response; AARE, amino acid-response element; ASNS, asparagine synthetase; BiP/GRP78, immunoglobulin heavy chain-binding protein/glucose-regulated protein 78; C/EBP, CCAAT/enhancer-binding protein; ChIP, chromatin immunoprecipitation; CHOP, C/EBP homology protein; ERSE, endoplasmic reticulum stress element; GAPDH, glyceraldehyde-3-phosphate dehydrogenase gene; GCN2, general control nonderepressible; HisOH, histidinol; LAP, liver-enriched activating protein; NSRE, nutrient sensing response element; PERK, double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase; qRT, quantitative real time; RT, reverse transcriptase; SNAT2, system A sodium-dependent neutral amino acid transporter 2; TBP, TATA-binding protein; TFII, general transcription factor; Tg, thapsigargin; UPR, unfolded protein response; XBP1, X-box binding protein 1; MEM, minimal essential medium; nt, nucleotide; siRNA, short interfering RNA; pol, polymerase; GTF, general transcription factor; hnRNA, heterogeneous nuclear RNA; bZIP, basic leucine zipper; ER, endoplasmic reticulum; CREB, cAMP-response-element-binding protein. kinases (1Wek R.C. Cavener D.R. Antioxid. Redox. Signal. 2007; 9: 2357-2371Crossref PubMed Scopus (223) Google Scholar). Phosphorylation of the translational initiation factor eIF2α at serine 51 by these kinases provokes a suppression of global protein synthesis and a paradoxical increase in the translation of selected mRNAs containing short upstream opening reading frames, including that of activating transcription factor 4 (ATF4) (2Vattem K.M. Wek R.C. Proc. Natl. Acad. Sci. U. S. A. 2004; 101: 11269-11274Crossref PubMed Scopus (1077) Google Scholar, 3Lu P.D. Harding H.P. Ron D. J. Cell Biol. 2004; 167: 27-33Crossref PubMed Scopus (633) Google Scholar). One of the eIF2α kinases is double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (PERK), which is activated by ER stress conditions, such as perturbation of calcium homeostasis, glucose deprivation, or other causes of misfolded protein accumulation in the ER lumen. Experimentally, the drugs tunicamycin (Tm), an inhibitor of N-glycosylation, or thapsigargin (Tg), an ER Ca2+-ATPase blocker, can also be used to induce the UPR (4Harding H.P. Zhang Y. Bertolotti A. Zeng H. Ron D. Mol. Cell. 2000; 5: 897-904Abstract Full Text Full Text PDF PubMed Scopus (1514) Google Scholar). PERK is one component of an adaptive response known as the unfolded protein response (UPR), which is comprised of three signal transduction pathways mediated by the ER membrane-resident stress PERK, and (4Harding H.P. Zhang Y. Bertolotti A. Zeng H. Ron D. Mol. Cell. 2000; 5: 897-904Abstract Full Text Full Text PDF PubMed Scopus (1514) Google Scholar, H.P. Zhang Y. Zeng H. Wek Ron D. Mol. Cell. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar, PubMed Scopus Google Scholar, D. J. PubMed Scopus Google Scholar, Cell Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). In to the UPR, amino acid to an increase in which binds to and the eIF2α kinase Cavener D.R. Wek R.C. 2000; PubMed Google Scholar, J. S. Wek K.M. Wek R.C. Cavener D.R. Mol. Cell. Biol. PubMed Scopus Google Scholar). This of is the amino acid response (AAR) of PERK or to the of target as a of increased ATF4 synthesis (1Wek R.C. Cavener D.R. Antioxid. Redox. Signal. 2007; 9: 2357-2371Crossref PubMed Scopus (223) Google Scholar). acid in in an increase in to translation the transcription of of which and D. Mol. Cell. Biol. PubMed Scopus Google Scholar, Cell. PubMed Scopus Google to as a in and revealed for and ATF4, including in amino acid and H.P. Zhang Y. Zeng H. P.D. Ron D. Mol. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). ATF4 is a of the of the basic leucine factor J. Cell Biol. PubMed Scopus Google Scholar). known to the as as other transcription including of the C/EBP However, ATF4 also including general transcription of kinase and transcription factor J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, S. S. A. Cell. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, S. A. PubMed Scopus Google Scholar). The of ATF4 to be and and a component of the adaptive AAR and UPR stress activation of transcription is mediated binding to a C/EBP-ATF genomic that is of for the C/EBP and J. PubMed Scopus Google Scholar). the target by ATF4 is SNAT2 (system A sodium-dependent neutral amino acid transporter the of SNAT2 gene and activity during amino acid deprivation, or D. PubMed Scopus Google Scholar, J. PubMed Scopus Google Scholar, 2004; PubMed Scopus Google Scholar). SNAT2 activity in the is by and in and other amino is to to the glucose in J. Biol. Full Text PDF PubMed Google Scholar). In system A is during the and is in and J. J. Biol. PubMed Scopus Google Scholar). adaptive by and as as increased in and in SNAT2 a gene is The nutrient sensing response and and in the promoter of human the activation of the gene by the AAR or the UPR pathway J. Biol. 2000; Full Text Full Text PDF PubMed Google Scholar, J. PubMed Scopus Google Scholar). The is a C/EBP-ATF site that binds ATF4 activation of the AAR or the UPR J. Biol. 2000; Full Text Full Text PDF PubMed Google Scholar, H. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). In contrast, the in the SNAT2 gene is of a that is also a C/EBP-ATF site but in by from the H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). ATF4 binding to the SNAT2 C/EBP-ATF site during AAR activation J. PubMed Scopus Google or not is ATF4 binding to SNAT2 during UPR activation not is to that despite the increased ATF4 synthesis known to during the UPR and the of an C/EBP-ATF site the SNAT2 gene, the SNAT2 and activity not in response to UPR activation H. K.M. J. PubMed Scopus Google Scholar). This was to the in the for control of the SNAT2 gene during UPR and AAR ATF4 to the SNAT2 C/EBP-ATF site during the ATF4 binding to the C/EBP-ATF site the that SNAT2 gene other of the general the SNAT2 gene during the The revealed that SNAT2 activity at the in the of ER stress despite increased synthesis of ATF4 and binding to the SNAT2 C/EBP-ATF site. revealed increase in histone H3 or general transcription factor recruitment to the SNAT2 promoter activation of the UPR Simultaneous activation of pathways that the UPR generates a signal that the SNAT2 transcription activity downstream of ATF4 binding. from ATF4 and An ATF4 by was used for ATF4 protein histone H3 and and histone at and from Cell human hepatoma and in minimal essential at in a of and The human cells, human human cells, and in amino and and to that or nutrient occurred to induce the UPR pathway, for a in glucose or containing thapsigargin or activate the AAR, in the amino acid or in or of the J. Biol. Full Text PDF PubMed Google and activation of the AAR K.M. U. PubMed Google Scholar, J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). that to of transcription J. Scopus Google Scholar, J. PubMed Scopus Google Scholar). deprivation, the was in HisOH, or for for was by a and of protein a to a the was to for and and and for at for ATF4 was a containing a the ATF4 at a of in for at The was for and for in and a and at a in for at The was in The was an and the to a of the a of an for was the including the to the was used to a the human SNAT2 4 and 4 the SNAT2 and the and and the and to the short heterogeneous nuclear This for activity is that by and Proc. Natl. Acad. Sci. U. S. A. 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PubMed Scopus Google Scholar). the of SNAT2 transcription activity in The of SNAT2 transcription was the UPR of the SNAT2 gene was and and increased SNAT2 transcription human and did not to ER the HepG2 human hepatoma and the cells, the SNAT2 to amino acid was and in transcription was as the that the UPR in (1Wek R.C. Cavener D.R. Antioxid. Redox. Signal. 2007; 9: 2357-2371Crossref PubMed Scopus (223) Google Scholar). the of the UPR the for SNAT2 transcription activity during UPR or AAR activation was in HepG2 hepatoma The revealed that the activity of the SNAT2 gene during AAR activation by to increase at at a and at the In contrast, activation of the UPR by Tg, the SNAT2 activity at 4 but by to the in the control The at and 4 also a control for the UPR, BiP/GRP78, a known gene H. H. J. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar, PubMed Scopus Google was In to that the to the transcription activity of the gene, which was at at and a of at This is in to the for SNAT2 during the UPR. J. PubMed Scopus Google was not to amino acid activity of the SNAT2 and in HepG2 human hepatoma during activation of the UPR or AAR HepG2 for in or the was and by The transcription activity was by the SNAT2 the 4 and the the The as to the control at The in for and from three as not the the The a from the control at of is by amino acid and ER A of in response to amino acid during which target gene by ATF4 is by a of The in transcription an increased synthesis of and and recruitment to the target gene H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, H. J. 2007; PubMed Scopus Google Scholar). in the protein of these three transcription factors AAR or UPR activation in HepG2 An increase in the ATF4 protein during the AAR or UPR occurred and the at was for stress stress pathways also the of as as the and at 4 and the The liver-enriched protein was also but the of was that for or at the SNAT2 C/EBP-ATF of ATF4, and binding to the human SNAT2 C/EBP-ATF site revealed an increase in ATF4 binding that a 4 and that was in of the AAR or the UPR stress signaling pathway activated ATF4 the human SNAT2 gene the transcription activity in the that is by ATF4 H. A. J. PubMed Scopus Google and that at an that of ATF4 H. J. 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PubMed Scopus Google Scholar, Y. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. 2007; PubMed Scopus Google Scholar). In the of H. H. Mol. Cell. Biol. 2000; PubMed Scopus Google that a promoter containing and a increase in transcription in response to UPR However, the a the of activity H. H. Mol. Cell. Biol. 2000; PubMed Scopus Google Scholar). can be to that the C/EBP-ATF site at promoter fragment to to the UPR. The of H. H. Mol. Cell. Biol. 2000; PubMed Scopus Google for be to and the present for UPR activation of SNAT2 in the of a ATF4 to activate the transcription from that a C/EBP-ATF site H. PubMed Scopus Google Scholar). The C/EBP-ATF site the of the SNAT2 gene as an AARE, activation of the gene amino acid J. PubMed Scopus Google Scholar). However, that ER stress also ATF4 the of or not ATF4 to the SNAT2 C/EBP-ATF site during ER stress The to is is known that SNAT2 and activity not increased to the increase in ATF4 protein ER stress in HepG2 H. K.M. J. PubMed Scopus Google Scholar). The present that ATF4 increased in UPR is to the SNAT2 C/EBP-ATF site at a to or that activation of the AAR pathway in HepG2 human hepatoma and of SNAT2 transcription during amino acid is by the binding and of ATF4, and at the SNAT2 C/EBP-ATF site J. PubMed Scopus Google Scholar). that the binding of these three factors at an synthesis H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google and of factor synthesis and recruitment in a for of C/EBP-ATF containing H. J. 2007; PubMed Scopus Google Scholar). ATF4 binding is at a component of the the of ATF4 recruitment histone including and the transcription activity H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). increased and binding to the C/EBP-ATF site and the of transcription H. J. Biol. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar, H. J. 2007; PubMed Scopus Google Scholar). the in show that the binding of three of these factors at the SNAT2 C/EBP-ATF site during ER that the recruitment of and be by ATF4, but is not histone of the general or transcription from the one the and quantitative binding of ATF4, and UPR activation is to that for the AAR binding during ER stress occurred at an during amino acid and binding was by a of a in SNAT2 However, of did not reverse the UPR of the SNAT2 gene, that is not a of that The of transcription activity from the SNAT2 gene activation of the UPR pathway the of was that increased transcription not ATF4 binding to the C/EBP-ATF site but also a activating be that amino acid ER stress was that the UPR pathway triggers a repressive signal for the SNAT2 gene, which the ATF4 binding and an of transcription for the from demonstrating that the of SNAT2 transcription by amino acid was by the activation of the UPR The of signal to be but as the the signal to chromatin of the and of the UPR did not the SNAT2 that of these transcription factors the or the for the of SNAT2 activation during ER histone and recruitment of general transcription factors was revealed that is an increase in histone H3 at the SNAT2 promoter and the C/EBP-ATF AAR activation but not UPR the that the present the SNAT2 promoter amino acid not UPR also that histone modification and of the at the SNAT2 promoter is an that to ATF4 binding. ATF4 to including TBP, and J. Biol. Full Text Full Text PDF PubMed Scopus Google and the of S. A. PubMed Scopus Google Scholar). of ATF4 enhances activation S. A. PubMed Scopus Google is that ATF4 a in the that the recruitment of containing histone activity not the ATF4 not histone modification and recruitment to the SNAT2 gene the was ER stress is not of was in to the SNAT2 gene, transcription from a reporter was UPR The of chromatin of a the UPR to the SNAT2 of the SNAT2 C/EBP-ATF site the by UPR that the response was the of In to in chromatin is that is a recruitment of a to the SNAT2 gene in response to the UPR that not activation of the AAR. for of the SNAT2 gene be a the the recruitment of the SNAT2 promoter to a transcription during AAR but not in the of ER also the in response the An of such a and of the of a gene a transcription is for the during A. PubMed Scopus Google Scholar, PubMed Scopus Google Scholar). such a for SNAT2, UPR activation of the these a SNAT2 activation by ATF4 and chromatin the of the SNAT2 C/EBP-ATF site to the AAR and UPR signals the of the chromatin is to that ATF4 is a factor that binds to the C/EBP-ATF site in a the of chromatin but a in The SNAT2 gene an to these and other control in response to stress and the signaling and of the for and