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The functionality of many cellular proteins depends on cofactors, yet they have only been implicated in a minority of Mendelian diseases. Here, we describe the first two inherited disorders of the cytosolic iron-sulfur protein assembly system

The human population is aging, and the need for interventions to slow progression of age-related diseases (geroprotective interventions) is growing. Repurposing compounds already used clinically, usually at modified doses, allows rapid implementation of geroprotective pharmaceuticals. Here we find the anti-retroviral nucleoside reverse transcriptase inhibitor (NRTI) zidovudine robustly extends lifespan and health span in C. elegans, independent of electron transport chain impairment or ROS accumulation. Rather, zidovudine treatment modifies pyrimidine metabolism and transcripts related to proteostasis. Testing regulators of mitochondrial stress and proteostasis shows that lifespan extension is dependent on activating transcription factor 4 (ATF-4). ATF-4 regulates longevity induced by mitochondrial stress, specifically communication between mitochondrial and cytosolic translation. Translation is reduced in zidovudine-treated worms, also dependent on ATF-4. Finally, we show ATF-4-dependent lifespan extension induced by didanosine, another NRTI. Altogether, our work elucidates the geroprotective effects of NRTIs such as zidovudine in vivo, via reduction of translation and ATF-4.

AbstractDihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disorder of the pyrimidine metabolism. Deficiency of this enzyme leads to an accumulation of thymine and uracil and a deficiency of metabolites distal to the catabolic enzyme. The disorder presents with a wide clinical spectrum, ranging from asymptomatic to severe neurological manifestations, including intellectual disability, seizures, microcephaly, autistic behavior, and eye abnormalities. Here, we report on an 11-year-old Malaysian girl and her 6-year-old brother with DPD deficiency who presented with intellectual disability, microcephaly, and hypotonia. Brain MRI scans showed generalized cerebral and cerebellar atrophy and callosal body dysgenesis in the boy. Urine analysis showed strongly elevated levels of uracil in the girl and boy (571 and 578 mmol/mol creatinine, respectively) and thymine (425 and 427 mmol/mol creatinine, respectively). Sequence analysis of the DPYDgene showed that both siblings were homozygous for the mutation c.1651G>A (pAla551Thr).© 2014 S. Karger AG, Basel

Dihydropyrimidine dehydrogenase DPD is the initial and ratelimiting enzyme in the catabolism of 5fluorouracil 5FU, and it is suggested that patients with a partial deficiency of this enzyme are at risk of developing severe 5FUassociated toxicity. We evaluated the importance of DPD deficiency, gender and the presence of the IVS141G>A mutation in the etiology of 5FU toxicity. In 61 of cases, decreased DPD activity could be detected in peripheral blood mononuclear cells. Furthermore, the number of females 65 in the total group of patients appeared to be higher than the number of males 35 p 0.03. Patients with partial DPD deficiency appeared to have a 3.4fold higher risk of developing grade IV neutropenia than patients with normal DPD activity. Analysis of the DPYDgene of patients suffering from grade IV neutropenia for the presence of the IVS141G>A mutation showed that 50 of the patients investigated were heterozygous or homozygous for the IVS141G>A mutation. Adopting a threshold level for DPD activity of 70 of that observed in the normal population, 14 of the population is prone to the development of severe 5FUassociated toxicity. Below this threshold level, 90 of individuals heterozygous for a mutation in the DPYDgene can be identified. Considering the common use of 5FU in the treatment of cancer, the severe 5FUrelated toxicities in patients with low DPD activity and the apparently high prevalence of the IVS141G>A mutation, screening of patients at risk before administration of 5FU is warranted. © 2002 WileyLiss, Inc.

Dihydropyrimidine dehydrogenase (DPD) deficiency is an autosomal recessive disease characterized by thymine-uraciluria in homozygous deficient patients. Cancer patients with a partial deficiency of DPD are at risk of developing severe life-threatening toxicities after the administration of 5-fluorouracil. Thus, identification of novel disease-causing mutations is of the utmost importance to allow screening of patients at risk. In eight patients presenting with a complete DPD deficiency, a considerable variation in the clinical presentation was noted. Whereas motor retardation was observed in all patients, no patients presented with convulsive disorders. In this group of patients, nine novel mutations were identified including one deletion of two nucleotides [1039-1042delTG] and eight missense mutations. Analysis of the crystal structure of pig DPD suggested that five out of eight amino acid exchanges present in these patients with a complete DPD deficiency, Pro86Leu, Ser201Arg, Ser492Leu, Asp949Val and His978Arg, interfered directly or indirectly with cofactor binding or electron transport. Furthermore, the mutations Ile560Ser and Tyr211Cys most likely affected the structural integrity of the DPD protein. Only the effect of the Ile370Val and a previously identified Cys29Arg mutation could not be readily explained by analysis of the three-dimensional structure of the DPD enzyme, suggesting that at least the latter might be a common polymorphism. Our data demonstrate for the first time the possible consequences of missense mutations in the DPD gene on the function and stability of the DPD enzyme.

Two different isoforms of subunit VIIa have been found in cytochrome coxidase isolated from human skeletal muscle. The first 22 residues of the N‐terminal amino acid sequences showed 5 differences. Our results provide the first conclusive evidence for the existence of cytochrome coxida isoenzymes in man. Since the two cytochrome coxidase isoforms were both present in skeletal muscle tissue, though not necessarily in the same cell type, this suggests that human cytochrome coxidase isoforms are not strictly tissue‐specific. These findings may have important implications for the elucidation of genetic diseases in man in which a deficiency of cytochrome coxidase is restricted to certain tissues.

Two different isoforms of subunit VIIa have been found in cytochrome coxidase isolated from human skeletal muscle. The first 22 residues of the N-terminal amino acid sequences showed 5 differences. Our results provide the first conclusive evidence for the existence of cytochrome coxida isoenzymes in man. Since the two cytochrome coxidase isoforms were both present in skeletal muscle tissue, though not necessarily in the same cell type, this suggests that human cytochrome coxidase isoforms are not strictly tissue-specific. These findings may have important implications for the elucidation of genetic diseases in man in which a deficiency of cytochrome coxidase is restricted to certain tissues.

Subunit VIII was purified from a preparation of the human heart cytochrome coxidase and its complete amino acid sequence was determined. The sequence proved to be much more related to that of the bovine liver oxidase subunit VIII than to that found in bovine heart. Our finding of a ‘liver-type’ subunit VIII in the human heart enzyme suggests that either there are no isoforms of human subunit VIII or the human oxidase does not show the type of tissue specificity that has been reported for the oxidase in other mammals.

Subunit VIII was purified from a preparation of the human heart cytochrome coxidase and its complete amino acid sequence was determined. The sequence proved to be much more related to that of the bovine liver oxidase subunit VIII than to that found in bovine heart. Our finding of a ‘liver‐type’ subunit VIII in the human heart enzyme suggests that either there are no isoforms of human subunit VIII or the human oxidase does not show the type of tissue specificity that has been reported for the oxidase in other mammals.