Adenosine diphosphate ribosylated histones.
Ontology highlight
ABSTRACT:
SUBMITTER: Ord MG
PROVIDER: S-EPMC1164544 | biostudies-other | 1977 Mar
REPOSITORIES: biostudies-other
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Project description:1. The effect of elongation factor 2 (EF 2) and of adenosine diphosphate-ribosylated elongation factor 2 (ADP-ribosyl-EF 2) on the shift of endogenous peptidyl-tRNA from the A to the P site of rat liver ribosomes (measured by the peptidyl-puromycin reaction) and on the release of deacylated tRNA (measured by aminoacylation) was investigated. 2. Limiting amounts of EF2, pre-bound or added to ribosomes, catalyse the shift of peptidyl-tRNA in the presence of GPT; when the enzyme is added in substrate amounts GMP-P(CH2)P [guanosine (beta, gamma-methylene)triphosphate] can partially replace GTP. ADP-ribosyl-EF 2 has no effect on the shift of peptidyl-tRNA when present in catalytic amounts, but becomes almost as effective as EF 2 when added in substrate amounts together with GTP; GMP-P(CH2)P cannot replace GTP. 3. The release of deacylated tRNA is induced only by substrate amounts of added EF 2 and also occurs in the absence of guanine nucleotides. In this reaction ADP-ribosyl-EF 2 is only 25% as effective as EF 2 in the absence of added nucleotide, but becomes 60-80% as effective in the presence of GTP or GMP-P(CH2)P. 4. The results obtained on protein-synthesizing systems are consistent with the hypothesis that ADP-ribosyl-EF 2 can operate a single round of translocation followed by binding of aminoacyl-tRNA and peptide-bond formation. 5. From the data obtained with the native enzyme it is concluded that the two moments of translocation require different conditions of interaction of EF 2 with ribosomes; it is suggested that the shift of peptidyl-tRNA is catalysed by EF 2 pre-bound to ribosomes, and that the release of tRNA is induced by a second molecule of interacting EF 2. The hydrolysis of GTP would be required for the release of pre-bound EF 2 from ribosomes. 5. The inhibition of the utilization of limiting amounts of EF 2 on ADP-ribosylation is very likely the consequence of a concomitant decrease in the rate of association and dissociation of the enzyme from ribosomes.
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Project description:Recently, the development of poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitors as a synthetic lethality approach has brought a major breakthrough in the treatment of breast cancer susceptibility gene (BRCA)-mutant cancers. Because sporadic cancers have also been found to commonly have other defects in DNA repair, PARP inhibitors are under active clinical investigation in combination with DNA-damaging therapeutics in a wide range of sporadic cancers. In this review, the authors discuss DNA repair mechanisms and PARP as a therapeutic target and summarize an update on clinical trials of available PARP inhibitors and predictive biomarkers for their efficacy.
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Project description:Extracellular nucleotides act as paracrine regulators of cellular signaling and metabolic pathways. Adenosine polyphosphate (adenosine triphosphate (ATP) and adenosine diphosphate (ADP)) release and metabolism by human hepatic carcinoma cells was therefore evaluated. Hepatic cells maintain static nanomolar concentrations of extracellular ATP and ADP levels until stress or nutrient deprivation stimulates a rapid burst of nucleotide release. Reducing the levels of media serum or glucose has no effect on ATP levels, but stimulates ADP release by up to 10-fold. Extracellular ADP is then metabolized or degraded and media ADP levels fall to basal levels within 2-4 h. Nucleotide release from hepatic cells is stimulated by the Ca(2+) ionophore, ionomycin, and by the P2 receptor agonist, 2'3'-O-(4-benzoyl-benzoyl)-adenosine 5'-triphosphate (BzATP). Ionomycin (10 ?M) has a minimal effect on ATP release, but doubles media ADP levels at 5 min. In contrast, BzATP (10-100 ?M) increases both ATP and ADP levels by over 100-fold at 5 min. Ion channel purinergic receptor P2X7 and P2X4 gene silencing with small interference RNA (siRNA) and treatment with the P2X inhibitor, A438079 (100 ?M), decrease ADP release from hepatic cells, but have no effect on ATP. P2X inhibitors and siRNA have no effect on BzATP-stimulated nucleotide release. ADP release from human hepatic carcinoma cells is therefore regulated by P2X receptors and intracellular Ca(2+) levels. Extracellular ADP levels increase as a consequence of a cellular stress response resulting from serum or glucose deprivation.
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Project description:Pancreatic cancer is the third most common cause of cancer death in the United States and eleventh worldwide. The majority of patients present with advanced disease with five-year overall survival of less than 10%. Traditional chemotherapy has been the mainstay treatment for years, with limited improvement in survival. Relative success has been achieved with agents targeting the DNA damage repair (DDR) mechanisms with poly adenosine diphosphate-ribose polymerase (PARP) inhibitors. The initial benefit was observed in patients with germline breast cancer-associated (BRCA) mutations. Multiple trials are now underway exploring PARP inhibitors in other DDR mutations such as the ataxia-telangiectasia mutated (ATM) gene and the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene (familial atypical multiple mole and melanoma syndrome), mismatch repair genes (Lynch syndrome), and others. PARP inhibitors are being evaluated as a single agent or combination chemotherapy, immunotherapy, and maintenance after chemotherapy. Here, we review current clinical trials targeting various DDR mutations and treatment strategies.
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Project description:An adenosine diphosphate sugar pyrophosphatase (ASPPase, EC ) has been characterized by using Escherichia coli. This enzyme, whose activities in the cell are inversely correlated with the intracellular glycogen content and the glucose concentration in the culture medium, hydrolyzes ADP-glucose, the precursor molecule of glycogen biosynthesis. ASPPase was purified to apparent homogeneity (over 3,000-fold), and sequence analyses revealed that it is a member of the ubiquitously distributed group of nucleotide pyrophosphatases designated as "nudix" hydrolases. Insertional mutagenesis experiments leading to the inactivation of the ASPPase encoding gene, aspP, produced cells with marginally low enzymatic activities and higher glycogen content than wild-type bacteria. aspP was cloned into an expression vector and introduced into E. coli. Transformed cells were shown to contain a dramatically reduced amount of glycogen, as compared with the untransformed bacteria. No pleiotropic changes in the bacterial growth occurred in both the aspP-overexpressing and aspP-deficient strains. The overall results pinpoint the reaction catalyzed by ASPPase as a potential step of regulating glycogen biosynthesis in E. coli.
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Project description:Stable cyclic adenosine 5'-diphosphate ribose (cADPR) analogues are chemical biology tools that can probe the Ca(2+) release mechanism and structure-activity relationships of this emerging potent second messenger. However, analogues with an intact "northern" ribose have been inaccessible due to the difficulty of generating the sensitive N1-ribosyl link. We report the first total synthesis of the membrane permeant, hydrolytically stable, cADPR receptor agonist 8-Br-N1-cIDPR via regio- and stereoselective N1-ribosylation of protected 8-bromoinosine.
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Project description:The development of colorectal cancer (CRC) can result from changes in a variety of cellular systems within the tumor microenvironment. Particularly, it is primarily associated with genomic instability that is the gradual accumulation of genetic and epigenetic changes consisting of a characteristic set of mutations crucial for pathways in CRC progression. Based on this background, the potential to focus on poly [adenosine diphosphate (ADP)-ribose] polymerase (PARP)-1 and poly-ADP ribosylation (PARylation) as the main causes of malignant formation of CRC may be considered. One of the important functions of PARP-1 and PARylation is its deoxyribonucleic acid (DNA) repair function, which plays a pivotal role in the DNA damage response and prevention of DNA damage maintaining the redox homeostasis involved in the regulation of oxidation and superoxide. PARP-1 and PARylation can also alter epigenetic markers and chromatin structure involved in transcriptional regulation for the oncogenes or tumor suppressor genes by remodeling histone and chromatin enzymes. Given the high importance of these processes in CRC, it can be considered that PARP-1 and PARylation are at the forefront of the pathological changes required for CRC progression. Therefore, this review addresses the current molecular biological features for understanding the multifactorial function of PARP-1 and PARylation in CRC related to the aforementioned roles; furthermore, it presents a summary of recent approaches with PARP-1 inhibition in non-clinical and clinical studies targeting CRC. This understanding could help embrace the importance of targeting PARP-1 and PARylation in the treatment of CRC, which may present the potential to identify various research topics that can be challenged both non-clinically and clinically.
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Project description:The binding of EF2 (elongation factor 2) and of ADP-ribosyl-EF 2 to rat liver ribosomes is inhibited by ricin. This result suggests that the native enzyme and its ADP-ribose derivative have the same or closely related binding sites on the ribosome. The inhibition by ricin of the binding of EF 2 to ribosomes is consistent with the previous observation that ricin affects EF 2-catalysed translocation during polypeptide chain elongation.
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Project description:Ovarian cancer is one of the leading causes of death from gynecologic cancers. In this present era of cancer treatment, therapeutic options for patients with advanced or recurrent ovarian cancer are limited. The present standard of care treatment for advanced ovarian cancer is a platinum-based doublet chemotherapy (paclitaxel and carboplatin with or without bevacizumab) after a maximum attempt of surgical cytoreduction. However, there are no promising options for the management of patients with ovarian cancer refractory to the platinum-based chemotherapy. Therefore, newer, safe, and more effective treatment modalities are required for patients with advanced or recurrent ovarian cancer. Poly(adenosine diphosphate [ADP]-ribose) polymerase (PARP) inhibitors have shown an impressive safety profile and anti-tumor efficacy in patients with breast cancer 1 and 2 (BRCA1 and BRCA2) gene-mutated ovarian cancer who were previously treated with the standard of care chemotherapy. We have done a detailed review of the literature to emphasize the role of PARP inhibitors in the treatment of advanced or relapsed ovarian cancer.
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Project description:Mycobacterium tuberculosis represents one of the world's most devastating infectious agents - with one third of the world's population infected and 1.5 million people dying each year from this deadly pathogen. As part of an effort to identify targets for therapeutic intervention, we carried out the kinetic characterization of the product of gene rv1700 of M. tuberculosis. Based on its sequence and its structure, the protein had been tentatively identified as a pyrophosphohydrolase specific for adenosine diphosphate ribose (ADPR), a compound involved in various pathways including oxidative stress response and tellurite resistance. In this work we carry out a kinetic, mutational and structural investigation of the enzyme, which provides a full characterization of this Mt-ADPRase. Optimal catalytic rates were achieved at alkaline pH (7.5-8.5) with either 0.5-1 mM Mg2+ or 0.02-1 mM Mn2+. K m and k cat values for hydrolysis of ADPR with Mg2+ ions are 200 ± 19 ?M and 14.4 ± 0.4 s-1, and with Mn2+ ions are 554 ± 64 ?M and 28.9 ± 1.4 s-1. Four residues proposed to be important in the catalytic mechanism of the enzyme were individually mutated and the kinetics of the mutant enzymes were characterized. In the four cases, the K m increased only slightly (2- to 3-fold) but the k cat decreased significantly (300- to 1900-fold), confirming the participation of these residues in catalysis. An analysis of the sequence and structure conservation patterns in Nudix ADPRases permits an unambiguous identification of members of the family and provides insight into residues involved in catalysis and their participation in substrate recognition in the Mt-ADPRase.
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