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Y Sanchez

Publications and source records attributed to Y Sanchez.

At least 37 records · Page 2Linked to original sources
PubMed1991

Hsp104 is a highly conserved protein with two essential nucleotide-binding sites.

Most eukaryotic cells produce proteins with relative molecular masses in the range of 100,000 to 110,000 after exposure to high temperatures. These proteins have been studied only in yeast and mammalian cells. In Saccharomyces cerevisiae, heat-shock protein hsp104 is vital for tolerance to heat, ethanol and other stresses. The mammalian hsp110 protein is nucleolar and redistributes with growth state, nutritional conditions and heat shock. The relationships between hsp110, hsp104 and the high molecular mass heat-shock proteins of other organisms were unknown. We report here that hsp104 is a member of the highly conserved ClpA/ClpB protein family first identified in Escherichia coli and that additional heat-inducible members of this family are present in Schizosaccharomyces pombe and in mammals. Mutagenesis of two putative nucleotide-binding sites in hsp104 indicates that both are essential for function in thermotolerance.

Amino Acid Sequence↗
PubMed1990

HSP104 required for induced thermotolerance.

A heat shock protein gene, HSP104, was isolated from Saccharomyces cerevisiae and a deletion mutation was introduced into yeast cells. Mutant cells grew at the same rate as wild-type cells and died at the same rate when exposed directly to high temperatures. However, when given a mild pre-heat treatment, the mutant cells did not acquire tolerance to heat, as did wild-type cells. Transformation with the wild-type gene rescued the defect of mutant cells. The results demonstrate that a particular heat shock protein plays a critical role in cell survival at extreme temperatures.

Cloning, Molecular↗
PubMed1990

Purification and characterization of the invertase from Schizosaccharomyces pombe. A comparative analysis with the invertase from Saccharomyces cerevisiae.

Invertase (EC 3.2.1.26) was purified to homogeneity from exponentially growing cells of Schizosaccharomyces pombe fully de-repressed for synthesis of the enzyme, and was shown to be a high-molecular-mass glycoprotein that can be dissociated in the presence of 8 M-urea/1% SDS into identical subunits with an apparent molecular mass of 205 kDa. The carbohydrate moiety, accounting for 67% of the total mass, is composed of equimolar amounts of mannose and galactose. There is a small amount of glucosamine, which is probably involved in the linkage to the protein moiety, since the enzyme is sensitive to treatment with endoglycosidase H. The composition of the carbohydrate moiety resembles that found in higher-eukaryotic glycoproteins and differs from glycoproteins found in Saccharomyces cerevisiae. The protein portion of each subunit is a polypeptide of molecular mass 60 kDa, very similar to the invertase of Sacch. cerevisiae. Both proteins cross-react with antibodies raised against the protein fractions of the other, indicating that the two enzymes are similar.

Carbohydrates↗
PubMed1989

DNA recognition element required for PUF-I mediated cell-type-specific transcription of the rat prolactin gene.

The cell-type-specific transcription of the prolactin gene in vitro is mediated through the interaction of prolactin upstream factor I (PUF-I) with a 28 basepair region of the gene promoter (-63 to -36) which contains an 18 bp A+T-rich imperfect palindrome (-63 to -46). Base substitutions were introduced into 16 of the 18 palindromic residues by targeted saturation mutagenesis. The GH3 binding and in vitro transcription assays of the mutated promoters showed that base substitutions within the 5'-ATATTCA-3' sequence located at -52 to -46 were detrimental to PUF-I binding and its cell-type-specific transcriptional enhancement activity. Transcription assays of the mutated promoters performed with several nonpituitary-derived extracts demonstrated that a distal TATA box located from -59 to -53 promotes initiation at -27. Thus, the cell-type-specific cis-acting element required by PUF-I for DNA recognition is immediately adjacent to a general TATA sequence. Base substitutions that decreased +1 transcription and PUF-I binding concomitantly increased -27 initiation of RNA in vitro. We suggest that PUF-I binding in pituitary cells potentiates +1 transcription and represses alternative TATA box activity for initiation events occurring at -27. This is the first known report of a eukaryotic DNA binding protein that has both an activator and repressor activity for a single transcription unit.

Animals↗
PubMed1986

Response to a hepatitis B polypeptide vaccine in micelle form in a young adult population.

Polypeptide micelles with relative molecular weights of 25,000 (p25) and 30,000 (gp30) daltons were prepared from native 22-nm hepatitis B surface antigen (HBsAg) particles. This p25/gp30 complex was alum-adsorbed, and three dosage levels (20 micrograms, 4 micrograms, and 0.8 micrograms) were administered at 0, 1, and 6 months to 51 human volunteers. Local and systemic reactions were clinically insignificant, and all vaccinees seroconverted, regardless of dose. As anticipated, antibody responses diminished as the dosage was reduced. Seroconversion rates and geometric mean antibody levels for the 20 micrograms dosage group were significantly better than those observed with a commercial vaccine and were comparable to those achieved after immunization with 40 micrograms of the intact 22-nm particles used to prepare the polypeptides. By 2 weeks, an anti-HBs response was elicited in 80% of the group receiving 20 micrograms of the polypeptide vaccine. This rapid response to immunization may be particularly beneficial for postexposure prophylaxis where the early development of immunity is advantageous.

Adult↗
PubMed1984

Enhancement of viral hepatitis B antibody (Anti-HBs) response to a synthetic cyclic peptide by priming with anti-idiotype antibodies.

In vivo injections of anti-idiotype antibodies were used to prime the immune system of mice to hepatitis B surface antigen (HBsAg). Anti-idiotype reagents in conjunction with a cyclic synthetic peptide analogous to positions 122-137 of HBsAg induced an antibody response to HBsAg (anti-HBs) comparable to that obtained with a single injection of intact HBsAg particles. In addition, high anti-HBs titers were produced in mice injected with HBsAg following anti-idiotype priming. These data indicate that anti-idiotype antibodies may be useful in priming the immune system of a host to a potential infectious agent.

Animals↗
PubMed1983

Immune response to hepatitis B surface antigen: enhancement by prior injection of antibodies to the idiotype.

Anti-idiotype reagents that recognize a common idiotype associated with the combining site of antibodies to hepatitis B surface antigen (anti-HBs) were used to manipulate the immune response to hepatitis B surface antigen in BALB/c mice. The injection of antibodies to the idiotype before antigenic stimulation resulted in an increase in the number of cells secreting immunoglobulin M antibodies to hepatitis B surface antigen. Anti-HBs-secreting cells were also induced by administration of antibodies to the idiotype without subsequent antigen exposure. These findings indicate that the immune response to hepatitis B surface antigen in mice is regulated through an idiotype-anti-idiotype network.

Animals↗
PubMed1983

Detection of interspecies idiotypic cross-reactions associated with antibodies to hepatitis B surface antigen.

A common idiotype was defined by a rabbit anti-idiotypic antiserum generated against human antibodies to hepatitis B surface antigen (anti-HBs). This idiotype was detected in anti-HBs from eight different individuals who had been previously infected with hepatitis B virus and is referred to as the CHBs idiotype. The CHBs idiotype was also identified in sera from rabbits, mice, guinea pigs, swine, goats and chimpanzees that had been immunized with hepatitis B surface antigen (HBsAg). Expression of the CHBs idiotype in sera from other species was associated with anti-HBs molecules. These results suggested that variable-region genes responsible for the CHBs idiotype have been conserved through long periods of evolution. It was noteworthy that the CHBs idiotype was not detected in the sera of a nonmammalian species, chickens, that had been successfully immunized with HBsAg.

Animals↗
PubMed1983

Comparative studies of the immunogenic activity of hepatitis B surface antigen (HBsAg) and HBsAg polypeptides.

Three hepatitis B surface antigen (HBsAg) preparations were compared: purified intact 22-nm HBsAg particles; HBsAg-derived, sodium dodecyl sulfate (SDS)-denatured P25 + GP30 polypeptide pool; and nondenatured P25 + GP30 micelles. The micelles had the same polypeptide composition as the P25 + GP30 pool. The immunogenicity in mice of each preparation, administered either in saline suspension or adsorbed to aluminum gel, was compared. The SDS-denatured polypeptides were less immunogenic than intact HBsAg particles, whereas the micelles were more immunogenic. High anti-HBs titers were observed in mice immunized with micelle preparations in either saline suspension or adsorbed to aluminum gel for as long as 200 days after a booster inoculation, administered 26 days after the primary dose.

Animals↗
PubMed1983

Development of sensitive immunoassays for detection of antibodies against hepatitis B surface antigen.

Three micro solid phase immunoassays (a micro-SPRIA and two ELISA techniques) were developed and tested for the detection of anti-HBs antibodies. Two different crosslinkers (glutaraldehyde and N-succinimidyl 3-(2-pyridyldithio) propionate) were used to couple a goat anti-mouse IgG reagent to alkaline phosphatase for use as enzyme-labeled probes in the two ELISA tests. With the latter crosslinker, a defined conjugate with a 1:1 antibody-enzyme molar ratio was obtained. The sensitivities of micro-SPRIA and the two types of ELISA were compared to that of the commercial solid phase radioimmunoassay AUSAB test. All three microtests were significantly more sensitive than the AUSAB test. The ELISA using the glutaraldehyde cross-linked conjugate was 3-5 times less sensitive than micro-SPRIA, while the ELISA using the disulfide-linked conjugate was 2.6-4.0 times more sensitive than micro-SPRIA.

Alkaline Phosphatase↗
PubMed1983

Characterization of anti-hepatitis B surface antigen monoclonal antibodies.

17 monoclonal antibodies generated against purified hepatitis B surface antigen (HBsAg), subtype ayw, were characterized by solid-phase radioimmunoassays. Eleven of these antibodies had specificity against the group-specific alpha determinant of HBsAg, two demonstrated antibody activity against the w HBsAg subtype, one against human serum albumin, and three against human IgG. All monoclonal antibodies were of the IgG class.

Antibodies, Monoclonal↗
PubMed1983

Epitopes associated with a synthetic hepatitis B surface antigen peptide.

A synthetic peptide (SP1), corresponding to the amino acid residues 122 through 137 of the major polypeptide derived from hepatitis B surface antigen (HBsAg), subtype ayw, was analyzed for the presence of the major epitopes of HBsAg. Both a cyclic form, produced by introduction of an intrachain disulfide bond, and a linear form of the peptide were characterized. A panel of monoclonal antibodies with defined specificity for the cross-reactive group a antigenic determinant(s) and for the y and w subtype specificities was used for this analysis. The cyclic, but not the linear, form of SP1 reacted with five of 14 anti-a monoclonal antibodies, demonstrating that the cyclic peptide contains a conformation-dependent a epitope. Only one anti-a antibody was found to react with both cyclic and linear forms of SP1. Because SP1 failed to react with the remaining 8 anti-a monoclonal antibodies, it was concluded that the a antigenic reactivity associated with HBsAg contains an additional epitope(s) unrelated to that expressed on SP1. Both cyclic and linear SP1 reacted with three of three anti-y monoclonal antibodies, indicating that a sequential y epitope is also present on SP1; no w reactivity was detected. Analysis of the idiotypes associated with the monoclonal antibodies showed those that combined with cyclic SP1 also inhibited the binding of a common human anti-HBs (CHBs) idiotype with its rabbit anti-idiotype serum, whereas a monoclonal antibody that did not react with the cyclic SP1 epitope failed to inhibit the CHBs idiotype-anti-idiotype reaction. Thus, the conformational a epitope present on cyclic SP1 appears to contain the predominant epitope recognized by humans in response to a natural HBV infection.

Animals↗
PubMed1982

Immunogenicity of conjugates and micelles of synthetic hepatitis B surface antigen peptides.

A cyclic peptide containing the amino acid sequence 122 through 137 of the major hepatitis B surface antigen (HBsAg) polypeptide was synthesized. The immunogenicity of this synthetic peptide, aggregated in micelles or covalently coupled to tetanus toxoid, was assessed in mice. Antibodies against HBsAg (anti-HBs) were obtained with both preparations, administered either in saline suspension or adsorbed on aluminum gel. The peptide-tetanus toxoid conjugate was more immunogenic than the peptide micelles, producing high levels of specific anti-HBs.

Animals↗
PubMed1981

Immunization of chimpanzees with hepatitis B virus-derived polypeptides.

Previous studies established that the purified polypeptides derived from the 22-nm particles associated with hepatitis B surface antigen (HBsAg) produce both humoral and cellular immunity against HBsAg in guinea pigs. Therefore, the two major polypeptides with molecular weights of 22,000 and 25,000 (P22 and P25, respectively) were isolated, adsorbed to an alum adjuvant, and used to immunize four nonimmune chimpanzees. A vigorous anti-HBs response was observed in all four animals after one inoculation of an alum-adsorbed polypeptide vaccine containing 40 micrograms of protein. After one to two booster inoculations, anti-HBs switched from being predominantly immunoglobulin M to the immunoglobin G class, indicating the establishment of immunological memory. Challenge of the vaccinated chimpanzees with 30,000 chimpanzee infectious doses of hepatitis B virus provided evidence for the efficacy of this vaccine. None of the four animals developed serological markers associated with an active hepatitis B infection, and no biochemical or histopathological changes of hepatitis were observed. A nonvaccinated control chimpanzee that was inoculated with the same hepatitis B virus material developed hepatitis B infection, confirming infectivity of the challenge inoculum.

Alanine Transaminase↗