RESUMO
Hypoxia signaling influences tumor development through both cell-intrinsic and -extrinsic pathways. Inhibiting hypoxia-inducible factor (HIF) function has recently been approved as a cancer treatment strategy. Hence, it is important to understand how regulators of HIF may affect tumor growth under physiological conditions. Here we report that in aging mice factor-inhibiting HIF (FIH), one of the most studied negative regulators of HIF, is a haploinsufficient suppressor of spontaneous B cell lymphomas, particular pulmonary B cell lymphomas. FIH deficiency alters immune composition in aged mice and creates a tumor-supportive immune environment demonstrated in syngeneic mouse tumor models. Mechanistically, FIH-defective myeloid cells acquire tumor-supportive properties in response to signals secreted by cancer cells or produced in the tumor microenvironment with enhanced arginase expression and cytokine-directed migration. Together, these data demonstrate that under physiological conditions, FIH plays a key role in maintaining immune homeostasis and can suppress tumorigenesis through a cell-extrinsic pathway.
Assuntos
Linfoma de Células B , Proteínas Repressoras , Animais , Camundongos , Hipóxia/metabolismo , Oxigenases de Função Mista/metabolismo , Proteínas Repressoras/metabolismo , Microambiente TumoralRESUMO
The aspariginyl hydroxylase human factor inhibiting hypoxia-inducible factor (FIH) is an important regulator of the transcriptional activity of hypoxia-inducible factor. FIH also catalyzes the hydroxylation of asparaginyl and other residues in ankyrin repeat domain-containing proteins, including apoptosis stimulating of p53 protein (ASPP) family members. ASPP2 is reported to undergo a single FIH-catalyzed hydroxylation at Asn-986. We report biochemical and crystallographic evidence showing that FIH catalyzes the unprecedented post-translational hydroxylation of both asparaginyl residues in "VNVN" and related motifs of ankyrin repeat domains in ASPPs (i.e., ASPP1, ASPP2, and iASPP) and the related ASB11 and p18-INK4C proteins. Our biochemical results extend the substrate scope of FIH catalysis and may have implications for its biological roles, including in the hypoxic response and ASPP family function.
Assuntos
Repetição de Anquirina , Oxigenases de Função Mista , Proteínas Repressoras , Proteínas Adaptadoras de Transdução de Sinal , Sequência de Aminoácidos , Proteínas Reguladoras de Apoptose , Catálise , Humanos , Hidroxilação , Hipóxia , Oxigenases de Função Mista/metabolismo , Proteínas Repressoras/metabolismoRESUMO
PURPOSE: Developmentally regulated Guanosine-5'-triphosphate-binding protein 1 (DRG1) is a highly conserved member of a class of GTPases implicated in translation. Although the expression of mammalian DRG1 is elevated in the central nervous system during development, and its function has been implicated in fundamental cellular processes, no pathogenic germline variants have yet been identified. Here, we characterize the clinical and biochemical consequences of DRG1 variants. METHODS: We collate clinical information of 4 individuals with germline DRG1 variants and use in silico, in vitro, and cell-based studies to study the pathogenicity of these alleles. RESULTS: We identified private germline DRG1 variants, including 3 stop-gained p.Gly54∗, p.Arg140∗, p.Lys263∗, and a p.Asn248Phe missense variant. These alleles are recessively inherited in 4 affected individuals from 3 distinct families and cause a neurodevelopmental disorder with global developmental delay, primary microcephaly, short stature, and craniofacial anomalies. We show that these loss-of-function variants (1) severely disrupt DRG1 messenger RNA/protein stability in patient-derived fibroblasts, (2) impair its GTPase activity, and (3) compromise its binding to partner protein ZC3H15. Consistent with the importance of DRG1 in humans, targeted inactivation of mouse Drg1 resulted in preweaning lethality. CONCLUSION: Our work defines a new Mendelian disorder of DRG1 deficiency. This study highlights DRG1's importance for normal mammalian development and underscores the significance of translation factor GTPases in human physiology and homeostasis.
Assuntos
Proteínas de Ligação ao GTP , Transtornos do Neurodesenvolvimento , Animais , Humanos , Camundongos , Proteínas de Transporte , GTP Fosfo-Hidrolases/genética , Mamíferos/metabolismo , Transtornos do Neurodesenvolvimento/genética , RNA MensageiroRESUMO
Hydroxylation is an emerging modification generally catalyzed by a family of â¼70 enzymes that are dependent on oxygen, Fe(II), ascorbate, and the Kreb's cycle intermediate 2-oxoglutarate (2OG). These "2OG oxygenases" sit at the intersection of nutrient availability and metabolism where they have the potential to regulate gene expression and growth in response to changes in co-factor abundance. Characterized 2OG oxygenases regulate fundamental cellular processes by catalyzing the hydroxylation or demethylation (via hydroxylation) of DNA, RNA, or protein. As such they have been implicated in various syndromes and diseases, but particularly cancer. In this review we discuss the emerging role of 2OG oxygenases in gene expression control, examine the regulation of these unique enzymes by nutrient availability and metabolic intermediates, and describe these properties in relation to the expanding role of these enzymes in cancer.
Assuntos
Regulação Neoplásica da Expressão Gênica , Neoplasias/genética , Animais , Metilação de DNA , Expressão Gênica , Humanos , Hidroxilação , Oxigenases de Função Mista/fisiologia , Neoplasias/metabolismo , Processamento de Proteína Pós-TraducionalRESUMO
Efficient stop codon recognition and peptidyl-tRNA hydrolysis are essential in order to terminate translational elongation and maintain protein sequence fidelity. Eukaryotic translational termination is mediated by a release factor complex that includes eukaryotic release factor 1 (eRF1) and eRF3. The N terminus of eRF1 contains highly conserved sequence motifs that couple stop codon recognition at the ribosomal A site to peptidyl-tRNA hydrolysis. We reveal that Jumonji domain-containing 4 (Jmjd4), a 2-oxoglutarate- and Fe(II)-dependent oxygenase, catalyzes carbon 4 (C4) lysyl hydroxylation of eRF1. This posttranslational modification takes place at an invariant lysine within the eRF1 NIKS motif and is required for optimal translational termination efficiency. These findings further highlight the role of 2-oxoglutarate/Fe(II) oxygenases in fundamental cellular processes and provide additional evidence that ensuring fidelity of protein translation is a major role of hydroxylation.
Assuntos
Regulação da Expressão Gênica , Histona Desmetilases/metabolismo , Oxigenases de Função Mista/química , Terminação Traducional da Cadeia Peptídica/genética , Fatores de Terminação de Peptídeos/química , Biossíntese de Proteínas , Sequência de Aminoácidos , Animais , Catálise , Linhagem Celular Tumoral , Códon de Terminação , Células HeLa , Humanos , Hidrólise , Hidroxilação , Histona Desmetilases com o Domínio Jumonji , Modelos Moleculares , Dados de Sequência Molecular , Processamento de Proteína Pós-Traducional , Estrutura Terciária de Proteína , Homologia de Sequência de AminoácidosRESUMO
GTPases are a large superfamily of evolutionarily conserved proteins involved in a variety of fundamental cellular processes. The developmentally regulated GTP-binding protein (DRG) subfamily of GTPases consists of two highly conserved paralogs, DRG1 and DRG2, both of which have been implicated in the regulation of cell proliferation, translation and microtubules. Furthermore, DRG1 and 2 proteins both have a conserved binding partner, DRG family regulatory protein 1 and 2 (DFRP1 and DFRP2), respectively, that prevents them from being degraded. Similar to DRGs, the DFRP proteins have also been studied in the context of cell growth control and translation. Despite these proteins having been implicated in several fundamental cellular processes they remain relatively poorly characterized, however. In this review, we provide an overview of the structural biology and biochemistry of DRG GTPases and discuss current understanding of DRGs and DFRPs in normal physiology, as well as their emerging roles in diseases such as cancer.
Assuntos
Proliferação de Células/fisiologia , Proteínas de Ligação ao GTP/metabolismo , Regulação da Expressão Gênica/fisiologia , Neoplasias/patologia , Animais , Proteínas de Ligação ao GTP/genética , Humanos , Microtúbulos/metabolismo , Biossíntese de Proteínas/fisiologia , Domínios Proteicos/fisiologia , Proteínas de Ligação a RNA/metabolismoRESUMO
Hypoxia-inducible transcription factors (HIFs) directly dictate the expression of multiple RNA species including novel and as yet uncharacterized long noncoding transcripts with unknown function. We used pan-genomic HIF-binding and transcriptomic data to identify a novel long noncoding RNA Noncoding Intergenic Co-Induced transcript (NICI) on chromosome 12p13.31 which is regulated by hypoxia via HIF-1 promoter-binding in multiple cell types. CRISPR/Cas9-mediated deletion of the hypoxia-response element revealed co-regulation of NICI and the neighboring protein-coding gene, solute carrier family 2 member 3 (SLC2A3) which encodes the high-affinity glucose transporter 3 (GLUT3). Knockdown or knockout of NICI attenuated hypoxic induction of SLC2A3, indicating a direct regulatory role of NICI in SLC2A3 expression, which was further evidenced by CRISPR/Cas9-VPR-mediated activation of NICI expression. We also demonstrate that regulation of SLC2A3 is mediated through transcriptional activation rather than posttranscriptional mechanisms because knockout of NICI leads to reduced recruitment of RNA polymerase 2 to the SLC2A3 promoter. Consistent with this we observe NICI-dependent regulation of glucose consumption and cell proliferation. Furthermore, NICI expression is regulated by the von Hippel-Lindau (VHL) tumor suppressor and is highly expressed in clear cell renal cell carcinoma (ccRCC), where SLC2A3 expression is associated with patient prognosis, implying an important role for the HIF/NICI/SLC2A3 axis in this malignancy.
Assuntos
Carcinoma de Células Renais/genética , Transportador de Glucose Tipo 3/genética , RNA Longo não Codificante/genética , Proteína Supressora de Tumor Von Hippel-Lindau/genética , Sistemas CRISPR-Cas/genética , Carcinoma de Células Renais/patologia , Linhagem Celular Tumoral , Proliferação de Células/genética , Proteínas de Ligação a DNA/genética , Regulação Neoplásica da Expressão Gênica/genética , Técnicas de Inativação de Genes , Humanos , Subunidade alfa do Fator 1 Induzível por Hipóxia/genética , Regiões Promotoras Genéticas/genética , RNA Polimerase II/genética , Ativação Transcricional/genética , Hipóxia Tumoral/genéticaRESUMO
Fe(II)/2-oxoglutarate (2OG)-dependent oxygenases are a conserved enzyme class that catalyse diverse oxidative reactions across nature. In humans, these enzymes hydroxylate a broad range of biological substrates including DNA, RNA, proteins and some metabolic intermediates. Correspondingly, members of the 2OG-dependent oxygenase superfamily have been linked to fundamental biological processes, and found dysregulated in numerous human diseases. Such findings have stimulated efforts to understand both the biochemical activities and cellular functions of these enzymes, as many have been poorly studied. In this review, we focus on human 2OG-dependent oxygenases catalysing the hydroxylation of protein and polynucleotide substrates. We discuss their modulation by changes in the cellular microenvironment, particularly with respect to oxygen, iron, 2OG and the effects of oncometabolites. We also describe emerging evidence that these enzymes are responsive to cellular stresses including hypoxia and DNA damage. Moreover, we examine how dysregulation of 2OG-dependent oxygenases is associated with human disease, and the apparent paradoxical role for some of these enzymes during cancer development. Finally, we discuss some of the challenges associated with assigning biochemical activities and cellular functions to 2OG-dependent oxygenases.
Assuntos
Dano ao DNA , Ácidos Cetoglutáricos/farmacologia , Oxigenases/metabolismo , Ácido Ascórbico/química , Fenômenos Biológicos , Catálise , DNA/química , Regulação da Expressão Gênica , Humanos , Hidroxilação , Hipóxia , Oxigenases de Função Mista/metabolismo , Modelos Moleculares , Neoplasias/metabolismo , Neoplasias/patologia , Oxirredução , Oxigênio/química , Processamento de Proteína Pós-Traducional , RNA/químicaRESUMO
Biochemical, structural and cellular studies reveal Jumonji-C (JmjC) domain-containing 7 (JMJD7) to be a 2-oxoglutarate (2OG)-dependent oxygenase that catalyzes (3S)-lysyl hydroxylation. Crystallographic analyses reveal JMJD7 to be more closely related to the JmjC hydroxylases than to the JmjC demethylases. Biophysical and mutation studies show that JMJD7 has a unique dimerization mode, with interactions between monomers involving both N- and C-terminal regions and disulfide bond formation. A proteomic approach identifies two related members of the translation factor (TRAFAC) family of GTPases, developmentally regulated GTP-binding proteins 1 and 2 (DRG1/2), as activity-dependent JMJD7 interactors. Mass spectrometric analyses demonstrate that JMJD7 catalyzes Fe(II)- and 2OG-dependent hydroxylation of a highly conserved lysine residue in DRG1/2; amino-acid analyses reveal that JMJD7 catalyzes (3S)-lysyl hydroxylation. The functional assignment of JMJD7 will enable future studies to define the role of DRG hydroxylation in cell growth and disease.
Assuntos
Biocatálise , GTP Fosfo-Hidrolases/metabolismo , Histona Desmetilases com o Domínio Jumonji/metabolismo , GTP Fosfo-Hidrolases/química , Humanos , Hidroxilação , Histona Desmetilases com o Domínio Jumonji/química , Modelos MolecularesRESUMO
In the version of this article initially published, authors Sarah E. Wilkins, Charlotte D. Eaton, Martine I. Abboud and Maximiliano J. Katz were incorrectly included in the equal contributions footnote in the affiliations list. Footnote number seven linking to the equal contributions statement should be present only for Suzana Markolovic and Qinqin Zhuang, and the statement should read "These authors contributed equally: Suzana Markolovic, Qinqin Zhuang." The error has been corrected in the HTML and PDF versions of the article.
RESUMO
Despite their importance, the molecular circuits that control the differentiation of naive T cells remain largely unknown. Recent studies that reconstructed regulatory networks in mammalian cells have focused on short-term responses and relied on perturbation-based approaches that cannot be readily applied to primary T cells. Here we combine transcriptional profiling at high temporal resolution, novel computational algorithms, and innovative nanowire-based perturbation tools to systematically derive and experimentally validate a model of the dynamic regulatory network that controls the differentiation of mouse TH17 cells, a proinflammatory T-cell subset that has been implicated in the pathogenesis of multiple autoimmune diseases. The TH17 transcriptional network consists of two self-reinforcing, but mutually antagonistic, modules, with 12 novel regulators, the coupled action of which may be essential for maintaining the balance between TH17 and other CD4(+) T-cell subsets. Our study identifies and validates 39 regulatory factors, embeds them within a comprehensive temporal network and reveals its organizational principles; it also highlights novel drug targets for controlling TH17 cell differentiation.
Assuntos
Diferenciação Celular/genética , Redes Reguladoras de Genes/genética , Células Th17/citologia , Células Th17/metabolismo , Animais , Células Cultivadas , DNA/genética , DNA/metabolismo , Fatores de Transcrição Forkhead/metabolismo , Técnicas de Silenciamento de Genes , Genoma/genética , Interferon gama/biossíntese , Interleucina-2/genética , Camundongos , Camundongos Endogâmicos C57BL , Nanofios , Proteínas de Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Reprodutibilidade dos Testes , Silício , Células Th17/imunologia , Fatores de Tempo , Transativadores/metabolismo , Fatores de Transcrição/metabolismo , Transcrição Gênica/genética , Receptor fas/metabolismoRESUMO
Hydroxylation is a novel protein modification catalyzed by a family of oxygenases that depend on fundamental nutrients and metabolites for activity. Protein hydroxylases have been implicated in a variety of key cellular processes that play important roles in both normal homeostasis and pathogenesis. Here, in this review, we summarize the current literature on a highly conserved sub-family of oxygenases that catalyze protein histidyl hydroxylation. We discuss the evidence supporting the biochemical assignment of these emerging enzymes as ribosomal protein hydroxylases, and provide an overview of their role in immunology, bone development, and cancer.
Assuntos
Oxigenases de Função Mista/metabolismo , Ribossomos/enzimologia , Animais , Histona Desmetilases/metabolismo , Humanos , Oxigenases de Função Mista/química , Músculo Esquelético/crescimento & desenvolvimento , Músculo Esquelético/metabolismo , Neoplasias/imunologia , Neoplasias/metabolismo , Neoplasias/patologia , Proteínas Nucleares/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas Ribossômicas/química , Proteínas Ribossômicas/metabolismoRESUMO
2-Oxoglutarate (2OG) and Fe(II)-dependent oxygenase domain-containing protein 1 (OGFOD1) is predicted to be a conserved 2OG oxygenase, the catalytic domain of which is related to hypoxia-inducible factor prolyl hydroxylases. OGFOD1 homologs in yeast are implicated in diverse cellular functions ranging from oxygen-dependent regulation of sterol response genes (Ofd1, Schizosaccharomyces pombe) to translation termination/mRNA polyadenylation (Tpa1p, Saccharomyces cerevisiae). However, neither the biochemical activity of OGFOD1 nor the identity of its substrate has been defined. Here we show that OGFOD1 is a prolyl hydroxylase that catalyzes the posttranslational hydroxylation of a highly conserved residue (Pro-62) in the small ribosomal protein S23 (RPS23). Unusually OGFOD1 retained a high affinity for, and forms a stable complex with, the hydroxylated RPS23 substrate. Knockdown or inactivation of OGFOD1 caused a cell type-dependent induction of stress granules, translational arrest, and growth impairment in a manner complemented by wild-type but not inactive OGFOD1. The work identifies a human prolyl hydroxylase with a role in translational regulation.
Assuntos
Proteínas de Transporte/metabolismo , Proteínas Nucleares/metabolismo , Prolil Hidroxilases/metabolismo , Biossíntese de Proteínas/fisiologia , Processamento de Proteína Pós-Traducional/fisiologia , Proteínas Ribossômicas/metabolismo , Análise de Variância , Proteínas de Transporte/genética , Biologia Computacional , Imunofluorescência , Técnicas de Silenciamento de Genes , Humanos , Hidroxilação , Immunoblotting , Imunoprecipitação , Ácidos Cetoglutáricos/metabolismo , Luciferases , Proteínas Nucleares/genética , Prolina/metabolismo , Biossíntese de Proteínas/genética , LevedurasRESUMO
The finding that oxygenase-catalyzed protein hydroxylation regulates animal transcription raises questions as to whether the translation machinery and prokaryotic proteins are analogously modified. Escherichia coli ycfD is a growth-regulating 2-oxoglutarate oxygenase catalyzing arginyl hydroxylation of the ribosomal protein Rpl16. Human ycfD homologs, Myc-induced nuclear antigen (MINA53) and NO66, are also linked to growth and catalyze histidyl hydroxylation of Rpl27a and Rpl8, respectively. This work reveals new therapeutic possibilities via oxygenase inhibition and by targeting modified over unmodified ribosomes.
Assuntos
Proteínas de Escherichia coli/metabolismo , Oxigenases de Função Mista/metabolismo , Oxigenases/metabolismo , Células Procarióticas/metabolismo , Ribossomos/metabolismo , Animais , Arginina/metabolismo , Proteínas Cromossômicas não Histona/metabolismo , Dioxigenases , Inibidores Enzimáticos/farmacologia , Escherichia coli/metabolismo , Proteínas de Escherichia coli/antagonistas & inibidores , Histidina/metabolismo , Histona Desmetilases , Humanos , Hidroxilação , Espectroscopia de Ressonância Magnética , Oxigenases de Função Mista/antagonistas & inibidores , Proteínas Nucleares/metabolismo , Oxigenases/antagonistas & inibidores , Proteínas Ribossômicas/metabolismoRESUMO
Eukaryotes have two paralogous developmentally regulated GTP-binding (DRG) proteins: DRG1 and DRG2, both of which have a conserved binding partner called DRG family regulatory protein 1 and 2 (DFRP1 and DFRP2), respectively. DFRPs are important for the function of DRGs and interact with their respective DRG via a conserved region called the DFRP domain. Despite being highly similar, DRG1 and DRG2 have strict binding specificity for their respective DFRP. Using AlphaFold generated structure models of the human DRG/DFRP complexes, we have biochemically characterized their interactions and identified interface residues involved in determining specificity. This analysis revealed that as few as five mutations in DRG1 can switch binding from DFRP1 to DFRP2. Moreover, while DFRP1 binding confers increased stability and GTPase activity to DRG1, DFRP2 binding only supports increased stability. Overall, this work provides new insight into the structural determinants responsible for the binding specificities of the DRG/DFRP complexes.
RESUMO
The hypoxic response in humans is mediated by the hypoxia-inducible transcription factor (HIF), for which prolyl hydroxylases (PHDs) act as oxygen-sensing components. The evolutionary origins of the HIF system have been previously unclear. We demonstrate a functional HIF system in the simplest animal, Trichoplax adhaerens: HIF targets in T. adhaerens include glycolytic and metabolic enzymes, suggesting a role for HIF in the adaptation of basal multicellular animals to fluctuating oxygen levels. Characterization of the T. adhaerens PHDs and cross-species complementation assays reveal a conserved oxygen-sensing mechanism. Cross-genomic analyses rationalize the relative importance of HIF system components, and imply that the HIF system is likely to be present in all animals, but is unique to this kingdom.
Assuntos
Fator 1 Induzível por Hipóxia/fisiologia , Oxigênio/fisiologia , Placozoa/fisiologia , Sequência de Aminoácidos , Animais , Dados de Sequência Molecular , Filogenia , Placozoa/genética , Pró-Colágeno-Prolina Dioxigenase/fisiologia , Ativação Transcricional , Proteína Supressora de Tumor Von Hippel-Lindau/fisiologiaRESUMO
Jumonji-C domain-containing protein 5 (JMJD5) is a 2-oxoglutarate (2OG)-dependent oxygenase that plays important roles in development, circadian rhythm, and cancer through unclear mechanisms. JMJD5 has been reported to have activity as a histone protease, as an Nε-methyl lysine demethylase, and as an arginine residue hydroxylase. Small-molecule JMJD5-selective inhibitors will be useful for investigating its (patho)physiological roles. Following the observation that the broad-spectrum 2OG oxygenase inhibitor pyridine-2,4-dicarboxylic acid (2,4-PDCA) is a 2OG-competing JMJD5 inhibitor, we report that 5-aminoalkyl-substituted 2,4-PDCA derivatives are potent JMJD5 inhibitors manifesting selectivity for JMJD5 over other human 2OG oxygenases. Crystallographic analyses with five inhibitors imply induced fit binding and reveal that the 2,4-PDCA C5 substituent orients into the JMJD5 substrate-binding pocket. Cellular studies indicate that the lead compounds display similar phenotypes as reported for clinically observed JMJD5 variants, which have a reduced catalytic activity compared to wild-type JMJD5.
Assuntos
Histonas , Neoplasias , Humanos , Ritmo Circadiano , Piridinas/farmacologia , Oxigenases/metabolismo , Histona Desmetilases com o Domínio Jumonji/metabolismoRESUMO
Although protein hydroxylation is a relatively poorly characterized posttranslational modification, it has received significant recent attention following seminal work uncovering its role in oxygen sensing and hypoxia biology. Although the fundamental importance of protein hydroxylases in biology is becoming clear, the biochemical targets and cellular functions often remain enigmatic. JMJD5 is a "JmjC-only" protein hydroxylase that is essential for murine embryonic development and viability. However, no germline variants in JmjC-only hydroxylases, including JMJD5, have yet been described that are associated with any human pathology. Here we demonstrate that biallelic germline JMJD5 pathogenic variants are deleterious to JMJD5 mRNA splicing, protein stability, and hydroxylase activity, resulting in a human developmental disorder characterized by severe failure to thrive, intellectual disability, and facial dysmorphism. We show that the underlying cellular phenotype is associated with increased DNA replication stress and that this is critically dependent on the protein hydroxylase activity of JMJD5. This work contributes to our growing understanding of the role and importance of protein hydroxylases in human development and disease.
Assuntos
Histona Desmetilases , Oxigenases de Função Mista , Humanos , Animais , Camundongos , Histona Desmetilases/genética , Oxigenases de Função Mista/genética , Oxigenases de Função Mista/metabolismo , Processamento de Proteína Pós-TraducionalRESUMO
Factor-inhibiting hypoxia-inducible factor (FIH) catalyzes the ß-hydroxylation of an asparagine residue in the C-terminal transcriptional activation domain of the hypoxia inducible factor (HIF), a modification that negatively regulates HIF transcriptional activity. FIH also catalyzes the hydroxylation of highly conserved Asn residues within the ubiquitous ankyrin repeat domain (ARD)-containing proteins. Hydroxylation has been shown to stabilize localized regions of the ARD fold in the case of a three-repeat consensus ankyrin protein, but this phenomenon has not been demonstrated for the extensive naturally occurring ARDs. Here we report that the cytoskeletal ankyrin family are substrates for FIH-catalyzed hydroxylations. We show that the ARD of ankyrinR is multiply hydroxylated by FIH both in vitro and in endogenous proteins purified from human and mouse erythrocytes. Hydroxylation of the D34 region of ankyrinR ARD (ankyrin repeats 13-24) increases its conformational stability and leads to a reduction in its interaction with the cytoplasmic domain of band 3 (CDB3), demonstrating the potential for FIH-catalyzed hydroxylation to modulate protein-protein interactions. Unexpectedly we found that aspartate residues in ankyrinR and ankyrinB are hydroxylated and that FIH-catalyzed aspartate hydroxylation also occurs in other naturally occurring AR sequences. The crystal structure of an FIH variant in complex with an Asp-substrate peptide together with NMR analyses of the hydroxylation product identifies the 3S regio- and stereoselectivity of the FIH-catalyzed Asp hydroxylation, revealing a previously unprecedented posttranslational modification.