Overexpression of Rad23 confers resistance to methylmercury in saccharomyces cerevisiae via inhibition of the degradation of ubiquitinated proteins.

We report here that overexpression of Rad23, a protein related to the ubiquitin-proteasome system, renders yeast cells resistant to methylmercury. Rad23 has three domains: two ubiquitin-associated (UBA) domains that bind to the multiubiquitin chain of ubiquitinated proteins and a single ubiquitin-like (UbL) domain that binds to proteasomes. To examine the mechanism of acquisition of methylmercury resistance that is induced by overexpression of Rad23, we expressed variants of Rad23 in which one or the other of the two types of domain was defective in yeast cells.

Overexpression of Bop3 confers resistance to methylmercury in Saccharomyces cerevisiae through interaction with other proteins such as Fkh1, Rts1, and Msn2.

We found that overexpression of Bop3, a protein of unknown function, confers resistance to methylmercury in Saccharomyces cerevisiae. Bmh2, Fkh1, and Rts1 are proteins that have been previously shown to bind Bop3 by the two-hybrid method. Overexpression of Bmh2 and the homologous protein Bmh1 confers resistance to methylmercury in yeast, but overexpression of either Fkh1 or Rts1 has a minimal effect.

Metal components analysis of metallothionein-III in the brain sections of metallothionein-I and metallothionein-II null mice exposed to mercury vapor with HPLC/ICP-MS.

Mercury vapor is effectively absorbed via inhalation and easily passes through the blood-brain barrier; therefore, mercury poisoning with primarily central nervous system symptoms occurs. Metallothionein (MT) is a cysteine-rich metal-binding protein and plays a protective role in heavy-metal poisoning and it is associated with the metabolism of trace elements. Two MT isoforms, MT-I and MT-II, are expressed coordinately in all mammalian tissues, whereas MT-III is a brain-specific member of the MT family.

Peroxiredoxin-mediated redox regulation of the nuclear localization of Yap1, a transcription factor in budding yeast.

A redox reaction involving cysteine thiol-disulfide exchange is crucial for the intracellular monitoring of oxidation status. The yeast transcription factor Yap1 is activated by formation of a disulfide bond, which inhibits nuclear export in response to peroxide stress, with resultant enhancement of the nuclear localization of Yap1. A glutathione peroxidase-like protein, Gpx3, which has peroxiredoxin activity, is required for formation of the disulfide bond in Yap1.

BCL-6 negatively regulates expression of the NF-kappaB1 p105/p50 subunit.

BCL-6 is a transcription repressor frequently deregulated in non-Hodgkin's B cell lymphomas. Its activity is also critical to germinal center development and balanced Th1/Th2 differentiation. Previous studies have suggested that NF-kappaB activity is suppressed in germinal center and lymphoma B cells that express high levels of BCL-6, and yet the reason for this is unknown.

A novel role for Bsd2 in the resistance of yeast to adriamycin.

In a search for undiscovered mechanisms of resistance to adriamycin, we screened a genomic library derived from Saccharomyces cerevisiae for genes related to adriamycin resistance. To our surprise, we found that overexpression of BSD2 rendered yeast cells resistant to adriamycin. Downregulation of the metal transporters Smf1 and Smf2 is the only activity of Bsd2 reported to date, and Bsd2 deficiency increases intracellular levels of Smf1 and Smf2.

Functions of yeast helicase Ssl2p that are essential for viability are also involved in protection from the toxicity of adriamycin.

We have found that, in the yeast Saccharomyces cerevisiae, overexpression of the DNA helicase Ssl2p confers resistance to adriamycin. Ssl2p is involved, as a subunit of the basic transcription factor TFIIH, in the initiation of transcription and in nucleotide-excision repair (NER), and this helicase is essential for the survival of yeast cells. An examination of the relationship between the known functions of Ssl2p and adriamycin resistance indicated that overexpression of Ssl2p caused little or no increase in the rate of RNA synthesis and in NER.

Promotion of microsatellite instability by hepatitis C virus core protein in human non-neoplastic hepatocyte cells.

Hepatitis C virus proteins exert an effect on a variety of cellular functions, including gene expression, signal transduction, and apoptosis, and because they possess oncogenic potentials, they have also been suggested to play an important role in hepatocarcinogenesis. Although the mechanisms of hepatocarcinogenesis remain poorly understood, we hypothesized that the disease may arise because of a disturbance of the DNA repair system by hepatitis C virus proteins. To test this hypothesis, we developed a reproducible microsatellite instability assay system for mismatch-repair using human-cultured cells transducted with pCXpur retrovirus expression vector, in which the puromycin resistance gene was rendered out-of-frame by insertion of a (CA)(17) dinucleotide repeat tract immediately following the ATG start codon.

Overexpression of Ssl2p confers resistance to adriamycin and actinomycin D in Saccharomyces cerevisiae.

Adriamycin is one of the most active anticancer drugs but the development of resistance to this drug hampers its efficacy. In an effort to identify novel genes that confer resistance to adriamycin, we introduced a yeast genomic library into Saccharomyces cerevisiae and selected transformants that grew in the presence of a normally toxic concentration of adriamycin. Detailed examination of a plasmid recovered from these transformants revealed that overexpression of the gene for Ssl2p rendered yeast cells resistant to adriamycin.

Differential activation of interferon-inducible genes by hepatitis C virus core protein mediated by the interferon stimulated response element.

We previously found that hepatitis C virus (HCV) core protein, which possesses the consensus sequence of genotype 1b, transcriptionally activates the interferon (IFN)-inducible 2'-5'-oligoadenylate synthetase (2'-5'-OAS) gene in human hepatocyte cells. To clarify the mechanism of this activation, we further characterized the core protein as an activator of the 2'-5'-OAS gene. We demonstrated that the activation of the 2'-5'-OAS gene by the core protein is a general phenomenon, regardless of HCV genotype and strain.

Citrate enhances the protective effect of orally administered bismuth subnitrate against the nephrotoxicity of cis-diamminedichloroplatinum.

Attenuation of the renal toxicity of cis-diamminedichloroplatinum (CDDP) is important in the use of this effective but cytotoxic anticancer agent. We have previously shown that the renal toxicity of CDDP can be efficiently reduced by the induction of metallothionein (MT) by preadministration of bismuth compounds in mice. Bismuth subnitrate (BSN) is used as an antigastric ulcer agent and as an antidiarrheic agent, and is suitable for inducing MT in the kidney in cancer patients.

Copper(II) protects yeast against the toxicity of cisplatin independently of the induction of metallothionein and the inhibition of platinum uptake.

We have made the unexpected discovery that copper sulfate protects Saccharomyces cerevisiae from the toxic effects of cisplatin. Addition of copper to the culture medium of yeast cells at concentrations above 0.1 microM significantly reduced the toxicity of cisplatin.

Modulation of adriamycin toxicity by tissue-specific induction of metallothionein synthesis in mice.

The effect of tissue specific induction of metallothionein (MT) by preadministration of metal compounds on the antitumor activity and adverse effects of adriamycin (ADR) was examined using mice bearing colon 38 adenocarcinoma. Significant increase in MT concentration was observed in the heart and bone marrow but not in the tumor tissue of the mice given bismuth (Bi) compound. Copper (Cu) increased MT in the tumor tissue but did not induce MT either in bone marrow or in the heart, whereas zinc (Zn) increased MT level in the heart and bone marrow as well as in the tumor tissue.

Identification of a lactoferrin-derived peptide possessing binding activity to hepatitis C virus E2 envelope protein.

Bovine and human lactoferrins (LF) prevent hepatitis C virus (HCV) infection in cultured human hepatocytes; the preventive mechanism is thought to be the direct interaction between LF and HCV. To clarify this hypothesis, we have characterized the binding activity of LF to HCV E2 envelope protein and have endeavored to determine which region(s) of LF are important for this binding activity. Several regions of human LF have been expressed and purified as thioredoxin-fused proteins in Escherichia coli.

Investigation of intracellular factors involved in methylmercury toxicity.

Methylmercury is a known pollutant that causes severe central nervous system disorders. It is capable of passing through the blood-brain barrier and accumulates in cerebral cells. However, little is known regarding the mechanism of its toxicity at the molecular level.

Negative autoregulation of BCL-6 is bypassed by genetic alterations in diffuse large B cell lymphomas.

Thirty to forty percent of diffuse large B cell lymphomas (DLBCL) carry BCL-6 translocations that disrupt its 5' regulatory region. This same region is also subject to somatic hypermutations, although only a small fraction of these mutations have a detectable effect on transcription. Here, we show that transcription of the BCL-6 gene is negatively self-regulated in multiple cell types.

Synthesis of betulin derivatives and their protective effects against the cytotoxicity of cadmium.

The protecting effect of betulin against cadmium toxicity was investigated using 11 kinds of analogues. It was elucidated by analyzing the analogue activities that both hydroxyl groups on C-3 and C-28 and the isopropenyl group on C-19 played important roles for expressing efficient activities. In addition, the cytotoxicity of betulin was also reduced by being functionalized using the above functional group.

Hepatitis C virus quasispecies in cancerous and noncancerous hepatic lesions: the core protein-encoding region.

We have shown that highly proofreading DNA polymerase is required for the polymerase chain reaction in the genetic analysis of hepatitis C virus (HCV). To clarify the status of HCV quasispecies in hepatic tissue using proofreading DNA polymerase, we performed a genetic analysis of the HCV core protein-encoding region in cancerous and noncancerous lesions derived from 4 patients with hepatocellular carcinoma. In contrast to the previously published data, we observed neither deletions nor stop codons in the analyzed region and no significant difference in the complexity of HCV quasispecies between cancerous and noncancerous lesions.

A ubiquitin-proteasome system is responsible for the protection of yeast and human cells against methylmercury.

The mechanism responsible for the toxic effects of methylmercury (MeHg), an important environmental pollutant, is poorly understood. We have identified a gene, CDC34, that confers resistance to MeHg in Saccharomyces cerevisiae by screening a yeast genomic DNA library. CDC34 encodes a ubiquitin-conjugating enzyme, Cdc34, which is involved in ubiquitin-dependent proteolysis.

[Recent advances of basic research and clinical application of lactoferrin as an antiviral reagent against chronic hepatitis C].

Hepatitis C virus(HCV), discovered in 1989, is the major causative agent of chronic viral hepatitis. Most patients progress to liver cirrhosis and hepatocellular carcinoma. In the therapy of hepatitis C, only interferon has been used effectively as an anti-HCV reagent in Japan, but its effectiveness is limited to about 30% of cases.

Overexpression of the ubiquitin-conjugating enzyme Cdc34 confers resistance to methylmercury in Saccharomyces cerevisiae.

A search was made for genes that confer resistance to methylmercury in yeast using a genomic DNA library derived from Saccharomyces cerevisiae. The genomic library was introduced into yeast and transformants that grew in the presence of a normally toxic concentration of methylmercury were selected. We sequenced the genomic DNA fragment in the plasmid from the clone with the highest resistance to methylmercury and analyzed the sequence for presence of an open reading frame that might confer resistance to methylmercury.

Glutathione content is correlated with the sensitivity of lines of PC12 cells to cisplatin without a corresponding change in the accumulation of platinum.

A study of the involvement of glutathione (GSH) in cellular resistance to cisplatin was performed using methylmercury-resistant sublines (PC12/TM series) of the PC12 line of rat pheochromocytoma cells. The seven clonal sublines of PC12 cells (PC12/TM, PC12/TM2, PC12/TM5, PC12/TM11, PC12/TM15, PC12/TM23, PC12/TM26) used in the study had intracellular levels of GSH that ranged from 8.7-39.