p53 codon 72 polymorphism and risk of cervical cancer

Storey et al. (1998) implicated the proline/argine polymorphism of the codon 72 of the tumor-suppressor gene p53 in the development of cervical cancer (CC) with the observation that the p53 protein is more efficiently inactivated by the E6 oncoprotein of human papillomavirus in p53 arginine as compared with its proline isoform. These authors further noted that in the United Kingdom, individuals homozygous for the arginine allele were several times more susceptible to HPV-associated tumorigenesis that proline/arginine heterozygotes. Subsequent studies in different countries failed to unanimously confirm this association. Motivated by the high incidence of CC in Chile, we undertook a case control study obtaining the following frequencies for genotypes PP, AP and AA in 60 ICC cases and 53 carefully selected controls: 0.067, 0.250, 0.683 and 0.075, 0.453, 0.472 respectively. A significant difference (X2 = 3.19 p < 0.02) and an odds ratio of 2.62 supported Storey et al (1998)'s results. In addition, rejecting previous hypotheses about the world distribution of the p53 codon 72 polymorphism, we conclude that this distribution most likely represents ancient human dispersal routes. Several methodological and biological explanations for the results obtained in previous negative association studies are briefly discussed.     

Effect of cigarette smoke on oral peroxidase activity in human saliva: role of hydrogen cyanide

Peroxidase activity in human saliva is composed of salivary peroxidase (80%), of salivary glandular origin, and myeloperoxidase (20%), of leukocyte origin. The term oral peroxidase (OPO) is used here to denote the total activity of both peroxidase species. Using the 2-nitrobenzoic acid-thiocyanate assay, OPO activity was measured in the saliva of nonsmokers after exposure to gas-phase cigarette smoke (CS) in an in vitro system using three puffs of CS in 1 h. A marked decrease of 76% of activity was observed following three puffs of CS. In order to elucidate the mechanism by which CS caused loss of OPO activity, several oxidants and antioxidants were applied to saliva in vitro in the presence and absence of CS. No protection for CS-induced loss of OPO activity occurred in the presence of glutathione, N-acetylcysteine, ascorbic acid, or Desferal. Exposure of saliva to purified aldehydes present in CS did not significantly affect OPO loss of activity. Similarly, ascorbic acid in the presence of FeCl(3) and nicotine also had no effect on OPO activity. Exposure of OPO to cyanate at levels present in CS caused a 65-70% loss of OPO activity, which was reversible after 24 h of dialysis. Moreover, hydroxocobalamin, a known cyanate chelator, could prevent CS- and potassium cyanide-induced inactivation of OPO by 70-90%. The results show that hydrogen cyanide, known to be present in microgram amounts per cigarette, is likely to be the species in CS responsible for loss of salivary OPO activity. The finding of reduced salivary OPO levels after CS exposure may represent a contributory mechanism for CS-related compromises in antimicrobial defenses in the aerodigestive tract.     

Characterization of a radish introgression carrying the Ogura fertility restorer gene Rfo in rapeseed,using the Arabidopsis genome sequence and radish genetic mapping

The radish Rfo gene restores male fertility in radish or rapeseed plants carrying Ogura cytoplasmic male-sterility. This system was first discovered in radish and was transferred to rapeseed for the production of F1 hybrid seeds. We aimed to identify the region of the Arabidopsis genome syntenic to the Rfo locus and to characterize the radish introgression in restored rapeseed. We used two methods: amplified consensus genetic markers (ACGMs) in restored rapeseed plants and construction of a precise genetic map around the Rfo gene in a segregating radish population. The use of ACGMs made it possible to detect radish orthologs of Arabidopsis genes in the restored rapeseed genome. We identified radish genes, linked to Rfo in rapeseed and whose orthologs in Arabidopsis are carried by chromosomes 1, 4 and 5. This indicates several breaks in colinearity between radish and Arabidopsis genomes in this region. We determined the positions of markers relative to each other and to the Rfo gene, using the progeny of a rapeseed plant with unstable meiotic transmission of the radish introgression. This enabled us to produce a schematic diagram of the radish introgression in rapeseed. Markers which could be mapped both on radish and restored rapeseed indicate that at least 50 cM of the radish genome is integrated in restored rapeseed. Using markers closely linked to the Rfo gene in rapeseed and radish, we identified a contig spanning six bacterial artificial chromosome (BAC) clones on Arabidopsis chromosome 1, which is likely to carry the orthologous Rfo gene.Electronic Supplementary Material Supplementary material is available in the online version of this article at Communicated by H. C. BeckerS. Giancola and S. Marhadour contributed equally to this work     

Structure and the energy of base pairing in non-natural bases of nucleic acids: the azaguanine-cytosine and azaadenine-thymine base pairs

Watson-Crick optimized geometries and the energies of base pairing for the natural pairs of nucleic bases: adenine-thymine (AT) and guanine-cytosine (GC) have been recalculated by ab initio methods in order to compare results to those found for the non-natural azaadenine-thymine (AAT) and azaguanine-cytosine (AGC) pairs. Geometry optimizations carried out at the HF/6-31G** level and energies obtained at MP2/6-31G**, show that AAT and AGC have hydrogen bonding patterns similar to the natural AT and GC and that the interaction energies (DeltaH0int) for the former are ca. 7 kcal/mol more stable than the latter. Accordingly, the pairs based on azapurines would be favored with respect to the natural pairs. Some possible explanations why nature does not use extensively the azabases in base pairing are given.     

Pig complement regulator factor H: molecular cloning and functional characterization

Complement is an efficient defense mechanism of innate immunity. Factor H is the central complement regulator of the alternative pathway, acting in the fluid-phase and on self surfaces. Pigs are considered a suitable source for xenotransplantation and thus several membrane-bound pig complement regulators with importance for the acute rejection phase have been investigated. However, pig fluid-phase regulators have not been described so far. We report the cloning, expression and functional characterization of pig factor H. After constructing a pig liver cDNA library, a full-length factor H cDNA was isolated and sequenced. The predicted protein is organized in 20 short consensus repeat (SCR) domains and has an overall identity of 62% to the human protein. For functional characterization, three deletion constructs of pig factor H were expressed in insect cells. Pig factor H construct SCR 1–4 has cofactor activity for factor I-mediated cleavage of human C3b, which is similar to the human regulator. In addition, this N-terminal construct binds to human C3b, while a construct consisting of SCR 15–20 showed a weaker binding to human C3b/C3d. Pig factor H has two major binding sites for heparin, as the two constructs representing SCR 1–7 and SCR 15–20 proteins, but not the SCR 1–4 protein, bind heparin. The C-terminal construct is able to bind to human endothelial cells, as assayed by FACS. We show that pig and human factor H share functional characteristics in complement regulation and cell surface binding. Possible consequences of using pig livers for xenotransplantation are discussed.The nucleotide sequence data reported are available in the EMBL database (accession number AJ278470)