Identification of SUMO modification sites in the base excision repair protein, Ntg1

DNA damaging agents are a constant threat to genomes in both the nucleus and the mitochondria. To combat this threat, a suite of DNA repair pathways cooperate to repair numerous types of DNA damage. If left unrepaired, these damages can result in the accumulation of mutations which can lead to deleterious consequences including cancer and neurodegenerative disorders. The base excision repair (BER) pathway is highly conserved from bacteria to humans and is primarily responsible for the removal and subsequent repair of toxic and mutagenic oxidative DNA lesions. Although the biochemical steps that occur in the BER pathway have been well defined, little is known about how the BER machinery is regulated. The budding yeast, Saccharomyces cerevisiae is a powerful model system to biochemically and genetically dissect BER. BER is initiated by DNA N-glycosylases, such as S. cerevisiae Ntg1. Previous work demonstrates that Ntg1 is post-translationally modified by SUMO in response to oxidative DNA damage suggesting that this modification could modulate the function of Ntg1. In this study, we mapped the specific sites of SUMO modification within Ntg1 and identified the enzymes responsible for sumoylating/desumoylating Ntg1. Using a non-sumoylatable version of Ntg1, ntg1ΔSUMO, we performed an initial assessment of the functional impact of Ntg1 SUMO modification in the cellular response to DNA damage. Finally, we demonstrate that, similar to Ntg1, the human homologue of Ntg1, NTHL1, can also be SUMO-modified in response to oxidative stress. Our results suggest that SUMO modification of BER proteins could be a conserved mechanism to coordinate cellular responses to DNA damage.

Identification and characterisation of alcohol-induced flushing in Caucasian subjects

The prevalence of the alcohol-flushing reaction was assessed in a group of healthy Caucasian medical students (200) by self-reporting and was found to occur in approximately 50% of female and 8% of male subjects. In most of the alcohol flushers there were other family members similarly affected. The presence of this side-effect after a small quantity of alcohol did not necessarily decrease the amount of alcohol consumed. A test dose of ethanol (0.4 g/kg body weight) confirmed the presence of the alcohol-induced flushing, which was of much shorter duration and intensity than that of the Oriental alcohol-induced flusher, as measured by laser Doppler velocimetry, and was not associated with high circulating concentrations of acetaldehyde. Topical administration of 5 M acetaldehyde showed an enhanced erythema in Caucasian flushers compared to non-flushing controls. This effect was not observed with topical ethanol. Low erythrocyte ALDH1 activity was found in all Caucasians (n = 30) who showed the alcohol-induced flushing reaction.

Acanthocytosis and haemolytic anaemia due to the McLeod blood group

A fourteen-year-old boy presenting with marked acanthocytosis of the red blood cells and a compensated haemolytic anaemia was shown to have the McLeod blood type. Only three other individuals have been reported as having this abnormality of the Kell blood group system without evidence of chronic granulomatous disease. Serological typing for the McLeod phenotype should be undertaken in males with unexplained acanthocytosis, and CPK estimation may provide a screening test for this condition.

Hereditary C2 deficiency associated with immune complex disease

A patient presenting with a syndrome probably due to immune complex deposition was investigated and found to possess an inherited C2 complement deficiency. Family studies indicated that the deficiency was transmitted as an autosomal recessive trait. HLA typing for the HLA-A and HLA-B specificities and HLA-D specificities indicated a close linkage between the HLA and C2 genes, as has been described elsewhere. The HLA-A and B locus specificities HLA-AW25 and HLA-B18 were coded for by each of the two chromosomes carrying the C2(0) gene. However, the two chromosomes differed at the HLA-D locus, as one coded for HLA-DW2 whilst the other did not. This case, therefore, provides a unique haplotype and may be of importance in mapping the C2(0) locus, as it suggests that the gene order on chromosome 6 is HLA-D, C2(0), HLA-B, HLA-A. Extensive complement component assays indicated that utilization of complement in the patient was occurring via the alternate complement pathway. It is suggested that, as a result of the C2 deficiency, infections with viruses and other agents could lead to an immune complex disease due to an impaired capacity to effectively eliminate circulating complexes.

Severe haemolytic anaemia complicating infectious mononucleosis

The case record of a patient suffering from infectious mononucleosis, complicated by severe haemolytic anaemia, with overt intravascular haemolysis, is reported. Investigation of such cases usually shows a high titre of cold agglutinins with anti-i specificity. In the case reported, the results of serological investigations were atypical, and suggested that cold agglutinins with anti-L activity (rather than anti-i) were predominant in the aetiology of the haemolysis.

Antibody detection and identification in a hospital blood bank

A six-year serological survey has demonstrated that an average of 2.2% per annum of individuals requiring compatibility testing possessed antibodies de novo and that the frequency for individuals forming antibodies following transfusion is 4.1%. The increased detection rate from 1.5% (1969) to 4.1% (1971-5) was almost entirely due to the sensitivity of the two-stage papain technique; a total of 124 antibodies were detected only in this test. Three of these enzyme-active antibodies were found to be the cause of mild haemolytic transfusion reactions. Since 60% of the listed 332 alloantibodies were Rh-specific, the transfusion of appropriately Rh phenotyped blood is strongly recommended.

Penicillin-induced haemolytic anaemia associated with microangiopathy

The development of a penicillin-induced haemolytic anaemia was studied in a patient with microangiopathy following an average daily dose of five million units of penicillin G (total dose 46 million units). It has been proposed that the combination of the benzylpenicilloyl hapten with exposed or altered erythrocyte antigens, induces an autoimmune response. In this particular case, it is suggested that erythrocyte membrane damage has predisposed to immune drug-mediated red cell damage.

Copper(II)-promoted solvolyses of nickel(II) complexes. I. N,N-Dialkyldithiocarbamates

The kinetics of copper(II)-promoted solvolyses of bis(N,N- dibutyldithiocarbamato)nickel(II) in dimethyl sulphoxide (dmso), N,N- dimethylacetamide (dma), acetone, and chloroform, and bis(N,N- dicyclohexyldithiocarbamato)nickel(II) in dmso and dma have been examined. Although the reaction stoichiometry differs in chloroform compared with the other solvents, in all media the two-term rate law ����������������� -d[Ni(dtc)2]/dt = (k1+k2[Cu2+])[Ni(dtc)2] is obeyed. However, in the absence of added sodium and nickel ions, experiments in dmso at low [Cu2+]O, indicate a negligible contribution from the k1 path. Results are discussed in the light of a mechanism involving primary dissociative (k1) and associative (k2) steps. Although the ratios k2/k1 indicate overall importance for the associative pathways of reaction in the low dielectric media cf. dmso and dma, the k1 term also appears as a significant contributor to the reaction of the dibutyldithiocarbamate complex in the former solvents.