Hydrogen peroxide-induced expression of the proto-oncogenes, c-jun, c-fos and c-myc in rabbit lens epithelial cells

The involvement of H2O2 in cataract development has been established in both human patients and animal models. At the molecular level H2O2 has been observed to cause damage to DNA, protein and lipid. To explore the oxidative stress response of the lens system at the gene expression level, we have examined the effects of H2O2 on the mRNA change of the proto-oncogenes, c-jun, c-fos and c-myc in a rabbit lens cell line, N/N1003A. H2O2 treatment of the rabbit lens epithelial cells for 60 min induces quick up-regulation of both c-jun and c-fos mRNAs. The maximal induction is 38 fold for c-jun at 150 microM and 72 fold for c-fos at 250 microM H2O2. Treatment of N/N1003A cells with 50-250 microM H2O2 for 60 min leads to a 2-5 fold increase of the c-myc mRNA level. H2O2 also induces an up-regulation in transactivity of the activating protein-1 (AP-1) as shown with a reporter gene driven by a prolactin gene promoter with 4 copies of AP-1 binding sites inserted in the upstream of the promoter. Maximal induction occurs with 150 microM H2O2. In the same system, the antioxidants, N-acetyl-cysteine (NAC) and pyrrolidine dithiocarbamate (PDTC) at concentrations shown to up-regulate the mRNAs of both c-jun and c-fos, also enhance the transactivity of AP-1. NAC and PDTC have different effects in modulating the induction of AP-1 activity by H2O2 and TPA. These results reveal that oxidative stress regulates expression of various regulatory genes in lens systems, which likely affects cell proliferation, differentiation and viability and thus affect normal lens functions.

High frequncies of fertilization and embryo formation in hexaploid wheat x Tripsacum dactyloides crosses

The Hexaploid wheat variety Fukuho was crossed with Tripsacum dactyloides (2n=4x=72). The total fertilization frequencies for the egg cell, polar nuclei, and both, were 58.3%, 26.8% and 58.9% of the 168 ovaries examined. However, the fertilization frequency of single polar nuclei was much lower at only 0.6%. The total frequency of fertilization was higher than that in wheat x maize crosses. A total of 49 hexaploid wheat varieties, including Hope carrying the dominant genes Kr1 and Kr2, were crossed with T. dactyloides, and most gave embryos. The embryoformation frequencies ranged from 0.5% to 59.0%. A higher frequency of 32.0% embryo formation was obtained following pollination of the variety Hope. In comparison with embryo formation in wheat x maize crosses the difference of embryo-formation frequencies between the two crosses was significant. The results of high frequencies of fertilization and embryo formation in wheat x T. dactyloides crosses indicated that the Kr genes are as inactive in wheat x T. dactyloides, as they are in wheat x maize crosses, and also that the efficiency of fertilization and embryo formation is higher in wheat x T. dactyloides than in what x maize crosses. The potential of wheat x T. dactyloides crosses for wheat haploid production and wheat improvement is discussed.

A year-round study on functional relationships of airborne fungi with meteorological factors

Air sampling was conducted in Waterloo, Canada throughout 1992. Functional relationships between aeromycota and meteorological factors were analysed. The meteorological factors were, in descending order of importance: mean temperature, minimum temperature, maximum temperature, mean wind speed, relative humidity (RH), rain, maximum wind speed and snow. The most important airborne fungal propagules in descending order were total fungal spores, unidentified Ascomycetes, Cladosporium, Coprinus, unidentified Basidiomycetes, Alternaria and unidentified fungi. Most airborne fungal taxa and highly significant relationship with temperature, but Aspergillus/Penicillium, hyphal fragments were positively associated with wind speed. In comparison with other airborne fungal taxa, Leptosphaeria and unidentified Ascomycetes were more closely correlated with rain and RH during the growing season.

Indoor aeromycota in relation to residential characteristics and allergic symptoms

The indoor aeromycota in several rooms of each of 15 residences in Kitchener-Waterloo, Ontario, Canada was studied from December 1991 to September 1993. There were significant differences in airborne spore concentrations among the types of rooms investigated. Numbers of airborne propagules were highest in the living rooms, followed by family rooms, kitchens, bathrooms and bedrooms. The highest fungal diversity was found in kitchens. Generally, presence of dampness and of carpets led to increased numbers of airborne spores. Forced air heating systems, humidifiers, air filters and air conditioners reduced concentrations of airborne fungi. Patients with respiratory allergies and known sensitivity to moulds reported allergic symptoms significantly less severe than average in residences with air conditioners, air filters, humidifers and forced air heating systems. In damp residences, their symptoms were significantly more severe than the average.

A mouse thymidylate synthase pseudogene derived from an aberrantly processed RNA molecule

A DNA fragment containing a mouse-thymidylate-synthase(TS) processed pseudogene was cloned and analyzed. Comparison with the sequences of the mouse TS-encoding gene (ts) and cDNA revealed that the pseudogene started at one of the normal 5' termini of TS mRNA, ended with a poly(A) tail, and was flanked by 16-nucleotide (nt) direct repeats. The region corresponding to the open reading frame was 97.3% identical to that of the cDNA. Two unusual features were observed. First, the poly(A) tail of the pseudogene was located 2 kb downstream from the normal location. Second, the final 10 nt of intron 5 were retained in the 'coding region' of the pseudogene. Therefore, it appears that the pseudogene was derived from a nonfunctional TS 'mRNA' that was aberrantly spliced and polyadenylated. Analysis of the sequence of intron 5 of the ts gene revealed the presence of an alternative 3' splice site 10 nt upstream from the normal splice site. S1-nuclease protection assays showed that about 10% of TS mRNA isolated from mouse cells was spliced at the alternative site.

Structure of the gene for mouse thymidylate synthase. Locations of introns and multiple transcriptional start sites

We have isolated and analyzed the structure of the gene for thymidylate synthase from a 5-fluoro-2'-deoxyuridine-resistant 3T6 cell line that overproduces thymidylate synthase 50-fold by virtue of gene amplification. Three overlapping DNA segments containing the entire thymidylate synthase gene were identified in Charon 35 genomic libraries. Sequence analysis revealed that all of the coding regions were contained in a 12-kilobase segment of DNA. The gene has 6 introns ranging from 0.6 to 4.1 kilobases in length. The sequences at the 5' and 3' ends of each intron conformed to the consensus sequences for mammalian introns. S1 nuclease and primer extension assays showed that transcription of the thymidylate synthase gene initiates at several sites within a 66-nucleotide region. There are no TATAA or CCAAT sequences in the vicinity of the initiation sites. However, the region does contain DNA sequences that are known to stimulate binding of the transcription factors Sp1 and USF. These binding sites are adjacent to each other, suggesting that the two proteins may bind to the upstream region of the thymidylate synthase gene in a cooperative or competitive manner.

Mouse thymidylate synthase messenger RNA lacks a 3' untranslated region

Analysis of the sequence of cDNA corresponding to mouse thymidylate synthase (5,10-methylenetetrahydrofolate:dUMP C-methyltransferase, EC 2.1.1.45) mRNA revealed that the termination codon TAA was followed immediately by a poly(A) sequence. This raised the possibility that mouse thymidylate synthase mRNA lacks a 3' untranslated region. In the present study, we have further investigated this possibility. DNA corresponding to the 3' end of the thymidylate synthase gene was isolated from a genomic library. The sequence of the genomic DNA was identical to that of the cDNA in the coding region. However, the termination codon was TAG in the genomic sequence rather than TAA, and poly(A) was not present in the genomic DNA. Sequences flanking the site of poly(A) addition were in good agreement with polyadenylylation consensus sequences. S1 nuclease analysis revealed that approximately 80% of the thymidylate synthase mRNA molecules were polyadenylylated at the termination codon. A secondary polyadenylylation site was detected 190-200 nucleotides downstream of the primary site. We conclude that the major species of mouse thymidylate synthase mRNA lacks a 3' untranslated region and that the final A of the termination codon is added by poly(A) polymerase. It appears that a 3' untranslated region is not essential for the accumulation or translation of this mRNA.

Extensive homology of nuclear ribonucleic acid and polysomal poly(adenylic acid) messenger ribonucleic acid between normal and neoplastically transformed cells

A cell line, designated BP6T, derived from Syrian hamster embryo (SHE) cells following treatment with benzo[a]pyrene is capable of producing tumors in newborn hamsters following the injection of as few as 1-10 cells. Polysomal poly(A) mRNA and total nuclear RNA obtained from this highly tumorigenic cell line were compared to RNAs obtained from the nonneoplastic parental embryo cells by a variety of techniques. RNA excess hybridizations to normal cell radiolabeled single-copy DNA or to a single-copy DNA tracer enriched for sequences transcribed in neoplastically transformed cells were unable to detect any significant differences in RNA sequence complexity between normal SHE cells and neoplastic BP6T cells. This finding of extensive homology of polysomal poly(A) mRNA and total nuclear RNA between normal and neoplastic cells, together with our previous finding of extensive homology of the major 35S-labeled nuclear or cytoplasmic polypeptides observable on two-dimensional gels [Leavitt, J. C., & Moyzis, R. K. (1978) J. Biol. Chem. 253, 2497-2500], demonstrates that the phenotypic changes associated with neoplastic transformation by chemical carcinogens are accompanied by relatively few changes in the qualitative pattern of gene expression in cells cultured in vitro.