tRNAPhe cleavage by aminoglycosides is triggered off by formation of an abasic site

This communication reports the characteristics of the mechanism of highly specific tRNA(Phe) cleavage, which occurs in the anticodon loop in the presence of aminoglycoside antibiotic-neomycin B. The data prove that the cleavage requires previous depurination of the polynucleotide chain at position 37, which is occupied by a hypermodified guanine base-wybutine. The results suggest that the phenomenon, previously considered as selective with respect to the presence of tRNA hypermodification, may concern far more RNA molecules, namely the ones carrying abasic sites.     

Curcumin treatment abrogates endoplasmic reticulum retention and aggregation-induced apoptosis associated with neuropathy-causing myelin protein zero-truncating mutants

Mutations in MPZ, the gene encoding myelin protein zero (MPZ), the major protein constituent of peripheral myelin, can cause the adult-onset, inherited neuropathy Charcot-Marie-Tooth disease, as well as the more severe, childhood-onset Dejerine-Sottas neuropathy and congenital hypomyelinating neuropathy. Most MPZ-truncating mutations associated with severe forms of peripheral neuropathy result in premature termination codons within the terminal or penultimate exons that are not subject to nonsense-mediated decay and are stably translated into mutant proteins with potential dominant-negative activity. However, some truncating mutations at the 3' end of MPZ escape the nonsense-mediated decay pathway and cause a mild peripheral neuropathy phenotype. We examined the functional properties of MPZ-truncating proteins that escaped nonsense-mediated decay, and we found that frameshift mutations associated with severe disease cause an intracellular accumulation of mutant proteins, primarily within the endoplasmic reticulum (ER), which induces apoptosis. Curcumin, a chemical compound derived from the curry spice tumeric, releases the ER-retained MPZ mutants into the cytoplasm accompanied by a lower number of apoptotic cells. Our findings suggest that curcumin treatment is sufficient to relieve the toxic effect of mutant aggregation-induced apoptosis and may potentially have a therapeutic role in treating selected forms of inherited peripheral neuropathies.     

GJB2 mutations and degree of hearing loss: a multicenter study

Hearing impairment (HI) affects 1 in 650 newborns, which makes it the most common congenital sensory impairment. Despite extraordinary genetic heterogeneity, mutations in one gene, GJB2, which encodes the connexin 26 protein and is involved in inner ear homeostasis, are found in up to 50% of patients with autosomal recessive nonsyndromic hearing loss. Because of the high frequency of GJB2 mutations, mutation analysis of this gene is widely available as a diagnostic test. In this study, we assessed the association between genotype and degree of hearing loss in persons with HI and biallelic GJB2 mutations. We performed cross-sectional analyses of GJB2 genotype and audiometric data from 1,531 persons, from 16 different countries, with autosomal recessive, mild-to-profound nonsyndromic HI. The median age of all participants was 8 years; 90% of persons were within the age range of 0-26 years. Of the 83 different mutations identified, 47 were classified as nontruncating, and 36 as truncating. A total of 153 different genotypes were found, of which 56 were homozygous truncating (T/T), 30 were homozygous nontruncating (NT/NT), and 67 were compound heterozygous truncating/nontruncating (T/NT). The degree of HI associated with biallelic truncating mutations was significantly more severe than the HI associated with biallelic nontruncating mutations (P<.0001). The HI of 48 different genotypes was less severe than that of 35delG homozygotes. Several common mutations (M34T, V37I, and L90P) were associated with mild-to-moderate HI (median 25-40 dB). Two genotypes--35delG/R143W (median 105 dB) and 35delG/dela(GJB6-D13S1830) (median 108 dB)--had significantly more-severe HI than that of 35delG homozygotes.     

Does the AD7c-NTP locus encode a protein?

AD7c-NTP, the only known protein entirely encoded by tandem and nested cassettes of Alu repetitive elements, is reportedly over-expressed in brains of Alzheimer's disease patients [de la Monte et al., J. Clin. Invest. 15 (1997)]. Based on these findings a commercial diagnostic assay ("7c Gold"/"AlzheimAlert" ) has been developed. We analyzed the published cDNA sequence and compared it to corresponding EST clones as well as the genomic sequences of human and chimpanzee. We come to the conclusion that the existence of the gene and in particular the predicted protein is inconsistent with EST and genomic data. Previously published data need to be reassessed.     

Cystatins, thyropins and inhibitors homologous to propeptides of cysteine proteases

Protein inhibitors of proteolytic enzymes play an important role in regulating the activity of endogenous proteases and in host defense mechanisms against pathogens preventing the deleterious effects of exogenous proteases. In recent years a great interest in protein inhibitors of cysteine proteases has increased due to the extensive growth of knowledge about the contribution of cysteine proteases to pathological processes associated with many human diseases, as well as due to prospects for treatment of these disorders which may arise from the thorough understanding of their inhibitory mechanisms. This paper reviews the most important aspects of three families of cysteine protease inhibitors: cystatins, thyropins and inhibitors homologous to propeptides of cysteine proteases. Special attention is given to structural bases of the interactions between the inhibitors and their target enzymes. The paper presents a general characterization of the families according to the MEROPS classification of protease inhibitors, pointing out new members.     

Molecular mechanisms of biotoxicity of homocysteine--facts and hypotheses

In the article, the main pathways of homocysteine metabolism are described, i.e. transsulfuration to cysteine and glutathione, as well as remethylation to methionine. Furthermore, formation of homocysteine thiolactone through editing mechanism with methionyl t-RNA syntethase and unusual reactivity of thiolactone against lysine epsilonNH2 groups of proteins as well as calcium dependent enzymatic hydrolysis of thiolactone are discussed. The effects of oxidative stress related to homocysteine are also reviewed. Finally, possible links of homocysteine to NO and arginine metabolism are discussed, including ADMA (N(G),N(G)-dimethylarginine). The links between metabolism of homocysteine, adenosine and other nucleosides are emphasized. In conclusion, the N-homocysteilation of proteins with thiolactone changing enormously their properties seems to be the main reason of biotoxicity of homocysteine during atherosclerosis and other diseases.     

Antibacterial and antifungal lysozyme-type activity in Cameraria ohridella pupae

Lysozyme-type antibacterial and antifungal activity in pupae of Cameraria ohridella was studied. Activity against Micrococcus luteus and Bacillus megaterium was detected in pupae extract. Also antifungal activity from C. ohridella pupae extract directed against Saccharomyces cerevisiae strain W 303 was shown. During immunoblotting two bands in pupae extract, with molecular mass of about 15 and 28 kDa were recognized by antibodies directed against HEWL. After acid electrophoresis followed by bioautography of the extract, two lytic zones showing lysozyme-type activity against M. luteus were observed. Two bacteria: Gram-positive Aerococcus viridans and Gram-negative Aeromonas salmonicida ssp. masoucida were isolated from pupae of C. ohridella. Their activity against M. luteus, B. megaterium, and S. cerevisiae W303 was detected. After immunoblotting with antibodies against HEWL, also two proteins from bacterial suspensions of A. viridans and A. salmonicida were detected, about 15 and 28 kDa.     

Mutator phenotype resulting from DNA polymerase IV overproduction in Escherichia coli: preferential mutagenesis on the lagging strand

We investigated the mutator effect resulting from overproduction of Escherichia coli DNA polymerase IV. Using lac mutational targets in the two possible orientations on the chromosome, we observed preferential mutagenesis during lagging strand synthesis. The mutator activity likely results from extension of mismatches produced by polymerase III holoenzyme.