Dimerization Binding Research Articles

Structures and Binding Energies of Nitrate Plasticizers DEGDN, TEGDN, and Nitroglycerine

AbstractThe interactions between nitrate plasticizer ingredients nitroglycerine, diethylene glycol dinitrate (DEGDN), and triethylene glycol dinitrate (TEGDN) have been investigated theoretically and experimentally. Density functional theory (DFT) and second order perturbation theory (MP2) calculations show that intermolecular N−O electrostatic interactions and hydrogen bonding between alkyl hydrogens and oxygen atoms govern the dimer structures, which have predicted binding energies ranging from 20.6 to 39.3 kJ mol−1. Vibrational frequencies observed in the nitrate band fingerprint region of the infrared spectra are in good agreement with the DFT scaled harmonic frequencies. The relative volatility observed in thermal gravimetric analysis (TGA) measurements of the pure ingredients and their 1 : 1 mixtures show reasonable correlation with the DFT dimer binding energies. The similarity in the dimer binding energies of all three plasticizers suggest that their mixtures should be uniformly miscible.

A Cooperative Folding Unit as the Structural Link for Energetic Coupling within a Protein.

Previously, we demonstrated that binding of a ligand to Escherichia coli cofactor-dependent phosphoglycerate mutase (dPGM), a homodimeric protein, is energetically coupled with dimerization. The equilibrium unfolding of dPGM occurs with a stable, monomeric intermediate. Binding of several nonsubstrate metabolites stabilizes the dimeric native form over the monomeric intermediate, reducing the population of the intermediate. Both the active site and the dimer interface appear to be unfolded in the intermediate. We hypothesized that a loop containing residues 118-152 was responsible for the energetic coupling between the dimer interface and the distal active site and was unfolded in the intermediate. Here, we investigated the structure of the dPGM intermediate by probing side-chain interactions and solvent accessibility of the peptide backbone. By comparing the effect of a mutation on the global stability and the stability of the intermediate, we determine an equilibrium φ value (φeq value), which provides information about whether side-chain interactions are retained or lost in the intermediate. Hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) was used to investigate differences in the solvent accessibility of the peptide backbone in the intermediate and native forms of dPGM. The results of φeq value analysis and HDX-MS reveal the least stable folding unit of dPGM, which is unfolded in the intermediate and links the active site to the dimer interface. The structure of the intermediate reveals how the cooperative network of residues in dPGM gives rise to the observed energetic coupling between dimerization and ligand binding.

Acidic Environment Induces Dimerization and Ligand Binding Site Collapse in the Vps10p Domain of Sortilin

Sortilin is a neuronal receptor involved in transmembrane signaling, endocytosis, and intracellular sorting of proteins. It cycles through a number of cellular compartments where it encounters various acidic conditions. The crystal structure of the sortilin ectodomain has previously been determined at neutral pH. Here, we present the 3.5-Å resolution crystal structure of sortilin at pH 5.5, which represents an environment similar to that of late endosomes, where ligands are released. The structure reveals an overall distortion of the 10-bladed β-propeller domain. This distortion and specific conformational changes, caused by protonation of a number of histidine residues, render the currently known binding sites unavailable for ligand binding. Access to the binding sites is furthermore blocked by a reversible and pH-dependent formation of tight sortilin dimers, also confirmed by electron microscopy, size-exclusion chromatography, and mutational studies. This study reveals how sortilin binding sites are disrupted and explains pH-dependent ligand affinity.

Production of Anti-c-Myc Monoclonal Antibody Inhibiting DNA Binding of c-Myc and Max Dimer by Epitope Peptide–CpG-DNA–Liposome Complex Without Carriers

The c-Myc protein is diversely involved in normal cellular function, and its deregulation has been implicated in several cancers. Therefore, c-Myc is a validated target for anti-cancer therapeutics. Here, we developed a monoclonal antibody specific to an epitope involved in the protein–protein interaction and DNA binding of c-Myc. We selected two candidate epitopes based on the antigenicity prediction and 3-D structure of c-Myc and successfully obtained a c-Myc-specific monoclonal IgG2a antibody clone. Based on the immunoprecipitation assay, the antibody recognized overexpressed c-Myc as well as endogenously expressed c-Myc in cell lines. The antibody co-immunoprecipitated Max showing that the antibody can recognize the c-Myc-Max heterodimer in solution. The results from the ELISA-based DNA binding assay revealed that treatment with the monoclonal antibody inhibits the binding activity of c-Myc. Therefore, we suggest that our anti-c-Myc monoclonal antibody can be used as a starting material for the development of an anti-cancer drug targeting c-Myc.

Non-canonical activation of OmpR drives acid and osmotic stress responses in single bacterial cells

Unlike eukaryotes, bacteria undergo large changes in osmolality and cytoplasmic pH. It has been described that during acid stress, bacteria internal pH promptly acidifies, followed by recovery. Here, using pH imaging in single living cells, we show that following acid stress, bacteria maintain an acidic cytoplasm and the osmotic stress transcription factor OmpR is required for acidification. The activation of this response is non-canonical, involving a regulatory mechanism requiring the OmpR cognate kinase EnvZ, but not OmpR phosphorylation. Single cell analysis further identifies an intracellular pH threshold ~6.5. Acid stress reduces the internal pH below this threshold, increasing OmpR dimerization and DNA binding. During osmotic stress, the internal pH is above the threshold, triggering distinct OmpR-related pathways. Preventing intracellular acidification of Salmonella renders it avirulent, suggesting that acid stress pathways represent a potential therapeutic target. These results further emphasize the advantages of single cell analysis over studies of population averages.

DNA-binding affinity and transcriptional activity of the RelA homodimer of nuclear factor κB are not correlated

The nuclear factor κB (NF-κB) transcription factor family regulates genes involved in cell proliferation and inflammation. The promoters of these genes often contain NF-κB-binding sites (κB sites) arranged in tandem. How NF-κB activates transcription through these multiple sites is incompletely understood. We report here an X-ray crystal structure of homodimers comprising the RelA DNA-binding domain containing the Rel homology region (RHR) in NF-κB bound to an E-selectin promoter fragment with tandem κB sites. This structure revealed that two dimers bind asymmetrically to the symmetrically arranged κB sites at which multiple cognate contacts between one dimer to the corresponding DNA are broken. Because simultaneous RelA-RHR dimer binding to tandem sites in solution was anti-cooperative, we inferred that asymmetric RelA-RHR binding with fewer contacts likely indicates a dissociative binding mode. We found that both κB sites are essential for reporter gene activation by full-length RelA homodimer, suggesting that dimers facilitate DNA binding to each other even though their stable co-occupation is not promoted. Promoter variants with altered spacing and orientation of tandem κB sites displayed unexpected reporter activities that were not explained by the solution-binding pattern of RelA-RHR. Remarkably, full-length RelA bound all DNAs with a weaker affinity and specificity. Moreover, the transactivation domain played a negative role in DNA binding. These observations suggest that other nuclear factors influence full-length RelA binding to DNA by neutralizing the transactivation domain negative effect. We propose that DNA binding by NF-κB dimers is highly complex and modulated by facilitated association-dissociation processes.

Molecular Modeling-Based Energy Analysis of Dimeric Binding of Ligands to the Minor DNA Groove

Molecular-modeling methods have been used to perform energy analysis of dimeric complex formation between lexitropsins and double-stranded DNA. Stabilization of dimeric complexes by hydrophobic and van der Waals interactions has been demonstrated. Electrostatic interactions and the contributions of hydrogen bonds and changes in the number of degrees of freedom had a destabilizing influence. The energy of monomeric and dimeric binding has been compared.

Heparin-bound chemokine CXCL8 monomer and dimer are impaired for CXCR1 and CXCR2 activation: implications for gradients and neutrophil trafficking.

Chemokine CXCL8 plays a pivotal role in host immune response by recruiting neutrophils to the infection site. CXCL8 exists as monomers and dimers, and mediates recruitment by interacting with glycosaminoglycans (GAGs) and activating CXCR1 and CXCR2 receptors. How CXCL8 monomer and dimer interactions with both receptors and GAGs mediate trafficking is poorly understood. In particular, both haptotactic (mediated by GAG-bound chemokine) and chemotactic (mediated by soluble chemokine) gradients have been implicated, and whether it is the free or the GAG-bound CXCL8 monomer and/or dimer that activates the receptor remains unknown. Using solution NMR spectroscopy, we have now characterized the binding of heparin-bound CXCL8 monomer and dimer to CXCR1 and CXCR2 receptor N-domains. Our data provide compelling evidence that heparin-bound monomers and dimers are unable to bind either of the receptors. Cellular assays also indicate that heparin-bound CXCL8 is impaired for receptor activity. Considering dimer binds GAGs with higher affinity, dimers will exist predominantly in the GAG-bound form and the monomer in the free form. We conclude that GAG interactions determine the levels of free CXCL8, and that it is the free, and not GAG-bound, CXCL8 that activates the receptors and mediates recruitment of blood neutrophils to the infected tissue.

Crystal structure of the Legionella pneumophila Lpg2936 in complex with the cofactor S-adenosyl-L-methionine reveals novel insights into the mechanism of RsmE family methyltransferases.

The methylation of U1498 located in the 16S ribosomal RNA of Escherichia coli is an important modification affecting ribosomal activity. RsmE methyltransferases methylate specifically this position in a mechanism that requires an S‐adenosyl‐L‐methionine (AdoMet) molecule as cofactor. Here we report the structure of Apo and AdoMet‐bound Lpg2936 from Legionella pneumophila at 1.5 and 2.3 Å, respectively. The protein comprises an N‐terminal PUA domain and a C‐terminal SPOUT domain. The latter is responsible for protein dimerization and cofactor binding. Comparison with similar structures suggests that Lpg2936 is an RsmE‐like enzyme that can target the equivalent of U1498 in the L. pneumophila ribosomal RNA, thereby potentially enhancing ribosomal activity during infection‐mediated effector production. The multiple copies of the enzyme found in both structures reveal a flexible conformation of the bound AdoMet ligand. Isothermal titration calorimetry measurements suggest an asymmetric two site binding mode. Our results therefore also provide unprecedented insights into AdoMet/RsmE interaction, furthering our understanding of the RsmE catalytic mechanism.

Saturation properties of helium drops from a leading-order description

Saturation properties are directly linked to the short-range scale of the two-body interaction of the particles. The case of helium is particular, from one hand the two-body potential has a strong repulsion at short distances. On the other hand, the extremely weak binding of the helium dimer locates this system very close to the unitary limit allowing for a description based on an effective theory. At leading order of this theory a two- and a three-body term appear, each one characterized by a low energy constant. In a potential model this description corresponds to a soft potential model with a two-body term purely attractive plus a three-body term purely repulsive constructed to describe the dimer and trimer binding energies. Here we analyse the capability of this model to describe the saturation properties making a direct link between the low energy scale and the short-range correlations. We will show that the energy per particle, $E_N/N$, can be obtained with reasonable accuracy at leading order extending the validity of this approximation, characterizing universal behavior in few-boson systems close to the unitary limit, to the many-body system.

Platelet-Derived Chemokine CXCL7 Dimer Preferentially Exists in the Glycosaminoglycan-Bound Form: Implications for Neutrophil-Platelet Crosstalk.

Platelet-derived chemokine CXCL7 (also known as NAP-2) plays a crucial role in orchestrating neutrophil recruitment in response to vascular injury. CXCL7 exerts its function by activating the CXC chemokine receptor 2 (CXCR2) receptor and binding sulfated glycosaminoglycans (GAGs) that regulate receptor activity. CXCL7 exists as monomers, dimers, and tetramers, and previous studies have shown that the monomer dominates at lower and the tetramer at higher concentrations. These observations then raise the question: what, if any, is the role of the dimer? In this study, we make a compelling observation that the dimer is actually the favored form in the GAG-bound state. Further, we successfully characterized the structural basis of dimer binding to GAG heparin using solution nuclear magnetic resonance (NMR) spectroscopy. The chemical shift assignments were obtained by exploiting heparin binding-induced NMR spectral changes in the WT monomer and dimer and also using a disulfide-linked obligate dimer. We observe that the receptor interactions of the dimer are similar to the monomer and that heparin-bound dimer is occluded from receptor interactions. Cellular assays also show that the heparin-bound CXCL7 is impaired for CXCR2 activity. We conclude that the dimer–GAG interactions play an important role in neutrophil–platelet crosstalk, and that these interactions regulate gradient formation and the availability of the free monomer for CXCR2 activation and intrathrombus neutrophil migration to the injury site.

CGAS senses long and HMGB/TFAM-bound U-turn DNA by forming protein-DNA ladders.

Cytosolic DNA arising from intracellular pathogens triggers a powerful innate immune response. It is sensed by cyclic GMP-AMP synthase (cGAS), which elicits the production of type I interferons by generating the second messenger 2'3'-cyclic-GMP-AMP (cGAMP). Endogenous nuclear or mitochondrial DNA can also be sensed by cGAS under certain conditions, resulting in sterile inflammation. The cGAS dimer binds two DNA ligands shorter than 20 base pairs side-by-side, but 20-base-pair DNA fails to activate cGAS in vivo and is a poor activator in vitro. Here we show that cGAS is activated in a strongly DNA length-dependent manner both in vitro and in human cells. We also show that cGAS dimers form ladder-like networks with DNA, leading to cooperative sensing of DNA length: assembly of the pioneering cGAS dimer between two DNA molecules is ineffective; but, once formed, it prearranges the flanking DNA to promote binding of subsequent cGAS dimers. Remarkably, bacterial and mitochondrial nucleoid proteins HU and mitochondrial transcription factor A (TFAM), as well as high-mobility group box 1 protein (HMGB1), can strongly stimulate long DNA sensing by cGAS. U-turns and bends in DNA induced by these proteins pre-structure DNA to nucleate cGAS dimers. Our results suggest a nucleation-cooperativity-based mechanism for sensitive detection of mitochondrial DNA and pathogen genomes, and identify HMGB/TFAM proteins as DNA-structuring host factors. They provide an explanation for the peculiar cGAS dimer structure and suggest that cGAS preferentially binds incomplete nucleoid-like structures or bent DNA.

An Unusual Dimeric Inhibitor of Acetylcholinesterase: Cooperative Binding of Crystal Violet.

Acetylcholinesterase (AChE) is an essential enzyme that terminates cholinergic transmission by a rapid hydrolysis of the neurotransmitter acetylcholine. AChE is an important target for treatment of various cholinergic deficiencies, including Alzheimer’s disease and myasthenia gravis. In a previous high throughput screening campaign, we identified the dye crystal violet (CV) as an inhibitor of AChE. Herein, we show that CV displays a significant cooperativity for binding to AChE, and the molecular basis for this observation has been investigated by X-ray crystallography. Two monomers of CV bind to residues at the entrance of the active site gorge of the enzyme. Notably, the two CV molecules have extensive intermolecular contacts with each other and with AChE. Computational analyses show that the observed CV dimer is not stable in solution, suggesting the sequential binding of two monomers. Guided by the structural analysis, we designed a set of single site substitutions, and investigated their effect on the binding of CV. Only moderate effects on the binding and the cooperativity were observed, suggesting a robustness in the interaction between CV and AChE. Taken together, we propose that the dimeric cooperative binding is due to a rare combination of chemical and structural properties of both CV and the AChE molecule itself.

Use of a Phosphorylation Site Mutant To Identify Distinct Modes of Gene Repression by the Control of Virulence Regulator (CovR) in Streptococcus pyogenes.

Control of the virulence regulator/sensor kinase (CovRS) two-component system (TCS) serves as a model for investigating the impact of signaling pathways on the pathogenesis of Gram-positive bacteria. However, the molecular mechanisms by which CovR, an OmpR/PhoB family response regulator, controls virulence gene expression are poorly defined, partly due to the labile nature of its aspartate phosphorylation site. To better understand the regulatory effect of phosphorylated CovR, we generated the phosphorylation site mutant strain 10870-CovR-D53E, which we predicted to have a constitutive CovR phosphorylation phenotype. Interestingly, this strain showed CovR activity only for a subset of the CovR regulon, which allowed for classification of CovR-influenced genes into D53E-regulated and D53E-nonregulated groups. Inspection of the promoter sequences of genes belonging to each group revealed distinct promoter architectures with respect to the location and number of putative CovR-binding sites. Electrophoretic mobility shift analysis demonstrated that recombinant CovR-D53E protein retains its ability to bind promoter DNA from both CovR-D53E-regulated and -nonregulated groups, implying that factors other than mere DNA binding are crucial for gene regulation. In fact, we found that CovR-D53E is incapable of dimerization, a process thought to be critical to OmpR/PhoB family regulator function. Thus, our global analysis of CovR-D53E indicates dimerization-dependent and dimerization-independent modes of CovR-mediated repression, thereby establishing distinct mechanisms by which this critical regulator coordinates virulence gene expression.IMPORTANCEStreptococcus pyogenes causes a wide variety of diseases, ranging from superficial skin and throat infections to life-threatening invasive infections. To establish these various disease manifestations, Streptococcus pyogenes requires tightly coordinated production of its virulence factor repertoire. Here, the response regulator CovR plays a crucial role. As an OmpR/PhoB family member, CovR is activated by phosphorylation on a conserved aspartate residue, leading to protein dimerization and subsequent binding to operator sites. Our transcriptome analysis using the monomeric phosphorylation mimic mutant CovR-D53E broadens this general notion by revealing dimerization-independent repression of a subset of CovR-regulated genes. Combined with promoter analyses, these data suggest distinct mechanisms of CovR transcriptional control, which allow for differential expression of virulence genes in response to environmental cues.

Tumor necrosis factor (TNF) signaling, but not TWEAK (TNF-like weak inducer of apoptosis)-triggered cIAP1 (cellular inhibitor of apoptosis protein 1) degradation, requires cIAP1 RING dimerization and E2 binding.

Tumor necrosis factor (TNF) signaling, but not TWEAK (TNF-like weak inducer of apoptosis)-triggered cIAP1 (cellular inhibitor of apoptosis protein 1) degradation, requires cIAP1 RING dimerization and E2 binding.

Synthesis of Naphthyridine Carbamate Dimer (NCD) Derivatives Modified with Alkanethiol and Binding Properties of G-G Mismatch DNA.

A series of new DNA binding molecules NCD-Cn-SH (n = 3, 4, 5, and 6) is reported, which possesses the NCD (naphthyridine carbamate dimer) domain selectively binding to the G-G mismatch in the 5'-CGG-3'/5'-CGG-3' sequence and a thiol moiety, which undergoes spontaneous dimerization to (NCD-Cn-S)2 upon oxidation under aerobic conditions. The S-S dimer (NCD-Cn-S)2 produced the 1:1 binding complex with improved thermal stability. The dimer binding to the CGG/CGG DNA showed higher positive cooperativity than the binding of monomer and previously synthesized NCTn derivative. The dimerization of NCD-Cn-SH was selectively accelerated on the CGG repeat DNA but not on the CAG repeat DNA.

Pancake Bond Orders of a Series of π‐Stacked Triangulene Radicals

AbstractConjugated radicals are capable of forming π‐stacking “pancake‐bonded” dimers. Members of the family of triangulene hydrocarbons, non‐Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake‐bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.

Pancake Bond Orders of a Series of π-Stacked Triangulene Radicals.

Conjugated radicals are capable of forming π-stacking "pancake-bonded" dimers. Members of the family of triangulene hydrocarbons, non-Kekulé neutral multiradicals, can utilize more than one singly occupied molecular orbital (SOMO) to form multiple pancake-bonded dimers with formal bond orders of up to five. The resulting dimer binding energies can be quite high and the intermolecular contacts rather small compared to the respective van der Waals values. The preferred configurations are driven by the large stabilization energy of overlapping SOMOs.

Abstract 4101: Targeting the EGFR/STAT3 axis in NSCLC with resistance to EGFR tyrosine kinase inhibitors using an oligonucleotide-based decoy

Abstract EGFR (Epidermal Growth Factor Receptor) is a major target for the treatment of Non-Small Cell Lung Cancer (NSCLC), but patients lacking EGFR mutation are insensitive to EGFR inhibition. Patients with EGFR mutations initially respond to EGFR tyrosine kinase inhibitors (TKIs), but eventually develop acquired resistance as a result of secondary mutations in the EGFR tyrosine kinase domain. Upregulation of Signal Transducer and Activator of Transcription (STAT3), a key oncogenic molecule in NSCLC that is downstream of EGFR signaling, contributes to intrinsic and acquired resistance to EGFR TKIs. In the clinic, agents targeting STAT3 have not been satisfactory to date. To address the limitations of available STAT3 inhibitors, we are currently testing a cyclic oligonucleotide molecule with a novel mechanism that acts as a STAT3 “decoy” (Cyclic STAT3 decoy, CS3D). CS3D mimics the DNA consensus sequence in the promoter region of STAT3-responsive genes, causing the binding of STAT3 dimers and preventing transcriptional regulation of STAT3-target genes. The effects of CS3D are compared to mutant cyclic STAT3 decoy (CS3M), which differs from CS3D by one base-pair. We have tested the ability of CS3D to produce anti-tumor effects in NSCLC cells that are EGFR WT (201T) and in EGFR mutant cells that also carry the T790M resistant mutation (H1975). Initial in vitro studies showed that CS3D caused a 50% inhibition in cell proliferation in 201T and H1975 relative to CS3M using MTS assays. Flow cytometry studies also demonstrated that CS3D caused a 2-fold increase in the percent of apoptotic cells as compared to CS3M. CS3D also caused a 2-fold reduction in expression of STAT3-target genes c-Myc, Bcl-xL and IL-6. Compared to CS3M, CS3D inhibited colony formation by 70%. Using an in vivo mouse xenograft model of 201T and H1975, CS3D caused a 96.5% reduction in tumor growth in 201T (P<0.007) compared to CS3M, while an 81.7% inhibition was seen in H1975 (P<.0001). Utilizing IHC, analysis of residual tumors also illustrated that CS3D induced more caspase3 cleavage relative to CS3M. Additionally, western blot analysis showed 70% reduction in c-Myc protein level in response to CS3D. These results suggest CS3D can be effective as a single therapeutic agent. Combining CS3D with EGFR inhibitors such as afatinib in vitro significantly suppressed cell viability by 85.2% and 80% in 201T and H1975 respectively, as compared to single treatment (CS3D alone reduced cell viability by 53%, and 51.5%, and afatinib alone reduced viability by 31.4% and 34.03% in 201T and H1975, respectively). The combination of CS3D and afatinib warrants further testing in vivo. These data suggest that CS3D alone or in combination with EGFR tyrosine kinase inhibitors produces anti-tumor effects in NSCLC with intrinsic and acquired resistance to EGFR TKIs. Supported by funding to the Masonic Cancer Center from the Minnesota 5th Order of Eagles. Citation Format: Christian Njatcha, Mariya Farooqui, Jennifer R. Grandis, Jill M. Siegfried. Targeting the EGFR/STAT3 axis in NSCLC with resistance to EGFR tyrosine kinase inhibitors using an oligonucleotide-based decoy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4101. doi:10.1158/1538-7445.AM2017-4101

Abstract 4501: CEBPD is an early endoplasmic reticulum stress response gene implicated in breast cancer cell survival

Abstract CEBPD (C/EBP delta) is a member of the CCAAT-enhancer binding protein (C/EBP) family of transcription factors characterized by a b-Zip domain that mediates dimerization and DNA binding. CEBPD is induced in response to acute stressors such as cytokine stimulation, bacterial lipopolysaccharide (LPS), corticosteroids, radiation and hypoxia. We have previously reported that CEBPD has dual functions in breast cancer by both attenuating or enhancing oncogenic pathways depending on context (Balamurugan and Sterneck, 2013, Mendoza-Villanueva et al., 2016). Recent studies reveal that elevated Endoplasmic Reticulum (ER) stress is associated with the pathology of several diseases including cancer. Limiting supply of nutrients and oxygen in growing tumor cells disrupts the protein folding homeostasis resulting in activation of the unfolded protein response (UPR). The UPR includes pathways that support adaptation to stress, and that are also implicated in promoting malignant features and therapy resistance in breast cancer. Hence, we investigated a possible role for CEBPD in this stress response pathway. Using breast cancer cell lines as model systems, we found that CEBPD is dynamically regulated in response to chemical and physiological inducers of ER stress. Kinetic analyses indicate that CEBPD induction is concurrent with the activation of the UPR effectors XBP1s and ATF4 suggesting a potential role in stress adaptation. Examination of the global transcriptional prolife of the Thapsigargin-induced stress response in MDA MB-231 cells indicated that CEBPD activates genes involved in cytokine and chemokine production/signaling, immune cell recruitment as well as angiogenesis pathways. While XBP1s has been previously ascribed to activating these pathways, the levels of activated XBP1 were not affected by CEBPD silencing. This is the first report of a similar role for CEBPD in the ER stress response and warrants the investigation of possible co-operation of CEBPD and XBP1 in the UPR pathway. Further, we show that knock down of CEBPD in cancer cells increased PARP cleavage and susceptibility to ER stress induced cell death. CEBPD deficient cells also displayed reduced LC3II accumulation, suggesting impaired autophagy induction in response to ER stress. Taken together, our data suggests that CEBPD is a novel proximal effector of the ER stress response in breast cancer cells. Activation of this transcription factor regulates tumor promoting inflammatory and angiogenic signaling pathways. Additionally, CEBPD expression confers a survival advantage to cancer cells encountering ER stress. Therefore, we propose that targeting CEBPD may sensitize cancer cells to ER stress inducing therapeutics. Citation Format: Namratha Sheshadri, Shikha Sharan, Esta Sterneck. CEBPD is an early endoplasmic reticulum stress response gene implicated in breast cancer cell survival [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4501. doi:10.1158/1538-7445.AM2017-4501