Cloning and characterization of a Saccharomyces cerevisiae gene encoding a new member of the ubiquitin-conjugating protein family

Ubiquitin-conjugating enzymes (E2s), which participate in the post-translational conjugation of ubiquitin to proteins, are encoded by a multigene family in the yeast Saccharomyces cerevisiae. E2s function in a variety of cellular activities including intracellular proteolysis, DNA repair, sporulation, and cell cycle traverse. Here, we report the cloning and characterization of a new member of the yeast UBC gene family, UBC8. UBC8 encodes a 206-amino acid protein containing a highly acidic carboxyl terminus. The primary structure of the protein is similar to that of all other known E2s, with the highest homology being to the E2 (23 kDa) of wheat germ. Haploid strains in which the UBC8 gene is disrupted are viable, and the disruption does not produce any obvious phenotype. The UBC8 protein, produced in Escherichia coli, forms thiol ester adducts with ubiquitin and, apparently, diubiquitin, but does not transfer ubiquitin to histones.

[An investigation on the resources of medicinal fungi in Sichuan]

This paper reports the classification, distributional traits, new distribution, specific species of medicinal fungi, as well as the status of anticancer medications and edible and medicinal fungi in Sichuan. Rational suggestions have been made with regard to the cultivation, development and utilization of those important species with proven curative effect.

CD4 monoclonal antibody pairs for immunosuppression and tolerance induction

A pair of rat anti-mouse CD4 monoclonal antibodies (mAb) have been selected which bind to different epitopes of the molecule. Both the mAb are rat IgG2b and show clear synergistic activity in complement lysis in vitro. When injected together in vivo, they exhibit an improved immunosuppressive effect, compared to each antibody alone, on allogeneic graft rejection, humoral responses and on tolerance induction. Limiting dilution analysis indicates that the in vivo depletion of interleukin 2-producing cells is improved using both mAb by 2-3-fold over that obtained with the individual antibodies. As little as 60 ng per mouse of the CD4 antibody pair was sufficient to allow the induction of tolerance to human gamma-globulin, even without elimination of the CD4+ cells. The results suggest that appropriate antibody pairs may be good candidates for effective immunosuppressive serotherapy in man.

Monoclonal antibodies to promote marrow engraftment and tissue graft tolerance

Allogeneic reactions are the major limitation to organ transplantation. These are manifested as rejection of the grafted tissue, and also, in the case of bone marrow transplantation (BMT), graft-versus-host disease (GVHD). Recent methods of avoiding GVHD, by depleting T cells from donor marrow, have led to an increased incidence of marrow graft rejection. Current recipient conditioning protocols involving drugs or irradiation cannot safely be increased, so alternatives must be found. Monoclonal antibodies can be used to control immune responses in vivo, and would be useful in this context if we could define and deplete the cells responsible for marrow rejection. We show here that elimination of residual L3T4+ and Lyt-2+ cells from mice receiving fully mismatched bone marrow abrogates rejection and promotes tolerance to donor-type skin grafts, even in sub-lethally irradiated recipients.

The chromosome 11 gene map: genes for growth and development, Wilms' tumor deletions, and cancer chromosome breakpoints

Human chromosome 11 is clearly a model autosome encoding genes and characteristics associated with both normal and abnormal growth and development, and several significant disorders. A fine-structure molecular, genetic, and physical map of this chromosome would add considerably to our knowledge of the organization and control of human genes and to an understanding of normal and abnormal human biology.

Influence of mouse liver stored vitamin A on the induction of mutations (Ames tests) and SCE of bone marrow cells by aflatoxin B1, benzo(a)pyrene, or cyclophosphamide

Male mice (C57BL/6J) at 2 weeks of age were divided into two groups and maintained on a vitamin A-deficient or vitamin A-(retinyl acetate) supplemented diet. After 8 weeks, the average liver vitamin A concentration of mice fed on vitamin A-deficient or -supplemented diet was 36 +/- 7 micrograms/g vs 287 +/- 22 micrograms/g, respectively. Uninduced liver S9 fractions were prepared from both groups of mice and used to activate (with cofactors) the precarcinogens aflatoxin B1 (AFB), cyclophosphamide (CPP), dimethylbenz(a)anthracene (DMBA), and benzo(a)pyrene (BP) in the Salmonella mutagenicity assay. S9 fraction prepared from both groups of mice failed to activate CPP to metabolites mutagenic in tester strains TA100 and TA1535 or to activate DMBA to metabolites mutagenic in TA100, but effectively activated AFB and BP to metabolites mutagenic in TA98. Comparison of activation activities of S9 prepared from liver of mice fed a high or low level of vitamin A was made with T98 treated with AFB or BP using three doses of S9 (50, 100, and 200 microliters/plate). S9 fractions from mice with a high liver vitamin A level were consistently less potent than S9 fractions from mice with a low liver vitamin A level in activating AFB to its mutagenic metabolites. This effect was not observed in BP-treated plates. Administration of AFB to groups of mice with a high liver vitamin A level induced significantly less SCE in bone marrow cells than did administration of AFB to mice with a low liver vitamin A level. This differential sensitivity was not observed when the two groups of mice were treated with either BP or CPP. The possible relationship between vitamin A levels in vivo and mutagenesis or carcinogenesis are discussed briefly.

Effect of retinoids on carcinogen-induced mutagenesis in Salmonella tester strains

The ability of retinol (Rol) in altering mutation frequencies induced by 7 carcinogens was studied in Salmonella/microsome assay using 4 tester strains namely TA98, TA100, TA102 and TA1535. The 7 carcinogens used were aflatoxin B1 (AFB), cyclophosphamide (CPP), 3-methylcholanthrene (MCA), benzo[a]pyrene (BP), benz[a]anthracene (BA), 9,10-dimethyl-1,2-benz[a]anthracene (DMBA) and mitomycin C (MMC). As reported previously, Rol significantly reduced the number of His+ revertants induced by AFB. It also reduced mutations induced by CPP or MCA but not that by BP, BA, DMBA or MMC. The abilities of Rol, retinoic acid, retinyl acetate and a known inhibitor for certain P-450 isozymes, 7,8-benzoflavone (BF) in inhibiting mutations caused by AFB and BP were studied and compared. All the 3 retinoids caused significant reduction of AFB-induced His+ revertants in a dose-dependent manner, but there was no effect on BP-induced mutation. BF strongly inhibited both AFB- and BP-induced revertants. The possibility of retinoids in exerting their effects on mutagenesis of precarcinogens by inhibiting only certain forms of cytochrome P-450 enzymes is discussed.

Influence of retinol on carcinogen-induced sister chromatid exchanges and chromosome aberrations in V79 cells

The influence of retinol (Rol) on sister chromatid exchanges (SCE) in V79 cells induced by six indirect and two direct carcinogens, and on chromosome aberration (CA) in V79 cells induced by four indirect carcinogens were studied. The indirect carcinogens used were aflatoxin B1 (AFB), cyclophosphamide (CPP), benzo(a)-anthracene (BA), benzo(a)pyrene (BP), 9,10-dimethyl-1,2-benz(a)anthracene (DMBA), and 3-methylcholanthrene (MCA). The two direct carcinogens were ethyl methane sulfonate (EMS) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Rol effectively inhibited SCE and CA induced by AFB and CPP in a dose-dependent manner, but it had no effect on SCE induced by BA, BP, DMBA, MCA, EMS, and MMNG. To the contrary, Rol had an enhancing effect on CA induced by BP and DMBA. Altering the concentration of the metabolic activation system-S9 mix had a significant effect on inhibition of AFB and CPP induced SCE by Rol. A high ratio of Rol/S9 mix resulted in a maximum effect of inhibition of SCE frequencies. Using low concentrations of S9 mix and various doses of Rol close to physiological levels (2 micrograms/ml and below) demonstrated a dose-dependent inhibition of AFB- and CPP-induced SCE. The possibility that Rol exerts its anticarcinogenic effects by inhibiting certain forms of the cytochrome P-450 isoenzymes required for activation of precarcinogens, such as AFB and CPP but not those enzymes required by BA, BP, DMBA, and MCA, is discussed.

A new method for sister-chromatid exchange studies in vivo, a single injection of BrdU in melted agar

Details are given for a new, rapid, and simple method of BrdU administration for SCE studies in vivo. BrdU was dissolved in melted agar and administered to mice as a single subcutaneous injection. Clear and reproducible sister chromatid differential staining of bone marrow cells was obtained. Melted agar, when injected into mice, solidified quickly and formed a clump which provided a sustained release of BrdU. HPLC analyses showed that a considerable serum level of BrdU was maintained for at least 10 h in a mouse injected with 25 mg of BrdU in agar.

Inhibition of retinoid toxicity by rat liver S9 fraction in cultured mammalian cells

The effects of retinol (Rol), retinyl acetate (RAc) or retinoic acid (RA) on growth of Chinese hamster V79 cells were studied. In addition, the effect of Rol on cell growth in the human lymphoid cell line RPMI no. 1788 was examined. Cultures were treated with retinoid alone, with retinoid plus S9 mix and with retinoid plus the supernatant of S9 fraction. Treatment of Rol, RAc or RA alone inhibited the growth of both cell lines as evidenced by a dose-dependent decrease of viable cell counts. Concurrent treatment of a retinoid with the well-known metabolic activation system S9 mix containing the rat liver S9 fraction plus enzyme cofactors resulted in a total elimination of the toxic effect of a retinoid. For instance, V79 cells treated with Rol, RAc or RA alone at the highest dose of 32 micrograms/ml, and human lymphoid cells treated with Rol at the highest dose of 24 micrograms/ml resulted in killing of over 90% of the cells, while addition of S9 mix to the cultures treated with such high doses of a retinoid showed no reduction of viable cells as compared with the controls. The supernatant of S9 fraction after high speed centrifugation also had dose-dependent protective effects against the toxicity of retinol in V79 cells. Finally, experiments using sucrose gradient centrifugation and [3H] Rol suggests that binding of a retinoid to its specific binding protein in the S9 mixture and supernatant greatly decreases or abolished the toxicity of free retinoid in cultured mammalian cells.