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P Valenzuela

Publications and source records attributed to P Valenzuela.

At least 73 records · Page 4Linked to original sources
PubMed1984

Nucleotide sequence of a yeast tRNAArg3A gene and its transcription in a homologous in vitro system.

Twelve bacterial clones containing complementary sequences to yeast tRNAArg3 were isolated from a gene library. The size of the yeast BamHI inserts ranges from 5.4 to 10 MDa. There are at least 6 copies of this gene in different loci of the yeast genome. Insert from clone pYAT-3 was mapped, and the presence of a tRNAArg3A gene was confirmed by DNA sequence. The coding region is colinear with the transcriptional product. Unlike other reported tRNAArg3A genes, this one is not linked to a tRNAAsp gene. In vitro transcription using a yeast extract produces a transcript of 76 +/- 1 bases.

Base Sequence↗
PubMed1984

Alpha-factor-directed synthesis and secretion of mature foreign proteins in Saccharomyces cerevisiae.

Saccharomyces cerevisiae cells were transformed with plasmids containing hybrid genes in which the sequence encoding mature human epidermal growth factor was joined to sequences encoding the leader region (preprosegment) of the precursor of the yeast mating pheromone alpha-factor. These cells accurately process the hybrid protein and efficiently secrete authentic biologically active human epidermal growth factor into the medium.

Amino Acid Sequence↗
PubMed1984

Primary structure and transcription of an amplified genetic locus: the CUP1 locus of yeast.

Copper resistance in yeast is controlled by the CUP1 locus. The level of resistance is proportional to the copy number of this locus, which can be found in up to 15 tandemly iterated copies. To elucidate the molecular mechanisms controlling the amplification and expression of the CUP1, locus, we determined its full nucleotide sequence. We have also identified and mapped two transcription units within the basic amplification unit of CUP1 in laboratory yeast strains. One of those transcription units is inducible by copper and encodes a low molecular weight copper binding protein--copper chelatin. The increased production of chelatin, due to both gene amplification and induction of transcription, leads to increased resistance of yeast cells to copper ions.

Amino Acid Sequence↗
PubMed1984

Cloning and analysis of integrated hepatitis virus sequences from a human hepatoma cell line.

We report here the isolation by molecular cloning and the analysis by heteroduplex and restriction enzyme mapping of seven distinct DNA fragments containing hepatitis B virus (HBV) sequences from genomic DNA of the PLC/PRF/5 human liver carcinoma cell line (the Alexander cell). No intact full-length HBV genomes were present. Three different patterns of organization of HBV fragments were detected. These included two linear fragments without detectable rearrangement, three other HBV fragments with internal deletions, and two HBV fragments containing long inverted duplications. HBsAg sequences are preferentially included in the integrated fragment, whereas the core gene is preferentially eliminated. Several of the integrated HBV fragments might act as templates for the synthesis of functional HBsAg mRNA, whereas only one clone could produce a full core antigen transcript.

Base Sequence↗
PubMed1983

Chemical synthesis of a gene for human epidermal growth factor urogastrone and its expression in yeast.

We have chemically synthesized and expressed in yeast a gene coding for human epidermal growth factor (urogastrone), a 53-amino-acid polypeptide that has been shown to promote epithelial cell proliferation and to inhibit gastric acid secretion. The synthetic gene, consisting of 170 base pairs, was designed with yeast-preferred codons and assembled by enzymatic ligation of synthetic fragments produced by phosphoramidite chemistry. The DNA synthesis protocol used allows for facile synthesis of oligonucleotides larger than 50 bases. Yeast cells were transformed with plasmids containing the synthetic gene under control of a yeast glyceraldehyde-3-phosphate dehydrogenase gene promoter and were shown to synthesize a biologically active human epidermal growth factor.

Amino Acid Sequence↗
PubMed1983

Synthesis of hepatitis B surface antigen in mammalian cells: expression of the entire gene and the coding region.

We have constructed two simian virus 40 early replacement recombinants that have the coding sequences for hepatitis B virus surface antigen (HBsAg). One construction, LSV-HBsAg, has the coding region for HBsAg but not the portion encoding the putative pre-surface antigen leader. Transformed monkey kidney cells (COS) infected with this recombinant express large quantities of the characteristic partially glycosylated HBsAg molecule, which are assembled into 22-nm particles that appear similar to those produced by human liver cells infected with hepatitis B virus. This result indicates that the pre-surface antigen sequences are not required for the synthesis of HBsAg or its assembly into particulate structures. The second recombinant, LSV-HBpresAg, has the entire surface antigen gene, including the putative promoter and pre-surface antigen region. COS cells infected with this recombinant plasmid produce 40- to 50-fold less HBsAg than those infected with the LSV-HBsAg recombinant plasmid. RNA mapping studies suggest that the transcription of the HBsAg gene is initiated at more than one site, or alternatively, that RNA splicing of transcripts occurs in the pre-surface antigen region.

Animals↗
PubMed1982

The reactivity of sulfhydryl groups of yeast DNA dependent RNA polymerase I.

The number of reactive cysteine residues of yeast RNA polymerase I was determined and their function was studied using parachloromercury benzoate (pCMB), dithiobisnitrobenzoate (DTNB) and N-ethyl-maleimide (NEM) as modifying agents. By treatment with DTNB about 45 sulfhydryl groups react in the presence of 8M urea. Under non-denaturing conditions only 20 sulfhydryl groups are reactive with pCMB and DTNB. Both reagents completely inactivate the enzyme and this effect can be reversed by reducing agents. The sedimentation coefficient and the subunit composition are not affected when the enzyme is inactivated. Two of the most reactive sulfhydryl groups are necessary for activity. The modification of these groups is partially protected by substrates and DNA, suggesting that they are involved either in catalysis or in the maintenance of the conformation of the active site. Experiments with 14C-NEM indicate that the most reactive groups are located in subunits of 185,000, 137,000 and 41,000 daltons.

Chloromercuribenzoates↗
PubMed1982

Synthesis and assembly of hepatitis B virus surface antigen particles in yeast.

The surface antigens of hepatitis B virus (HBsAg) has been synthesized in the yeast Saccharomyces cerevisiae by using an expression vector that employs the 5'-flanking region of yeast alcohol dehydrogenase I as a promotor to transcribe surface antigen coding sequences. The protein synthesized in yeast is assembled into particles having properties similar to the 22-nm particles secreted by human cells.

Alcohol Dehydrogenase↗
PubMed1982

Isolation and structure of a yeast initiator tRNAmet gene.

Sixteen bacterial clones containing yeast initiator tRNAmet genes have been isolated. The size of the BamHI fragments encoding these genes ranges from 4,000 to 23,000 base pairs. The nucleotide sequence of one member of this group has been determined. It has no intervening sequences.

Base Composition↗
PubMed1982

Rat preprocarboxypeptidase A: cDNA sequence and preliminary characterization of the gene.

Rat carboxypeptidase A cDNA clones have been isolated from a cDNA library prepared from pancreatic mRNA. An almost complete mRNA sequence has been deduced that predicts a polypeptide having 78% amino acid sequence homology with bovine carboxypeptidase A. The amino acid sequence of the activation and signal peptides of the carboxypeptidase A precursor were inferred from the nucleotide sequence. The cDNA was used as a probe to identify DNA fragments containing carboxypeptidase A sequences in a bacteriophage lambda library of rat genomic DNA. Heteroduplexes revealed that the DNA coding sequence occupies 5.5 kilobases and is interrupted by nine intervening sequences. The nucleotide sequence of the 5' end of the gene and the adjacent flanking region provides information on the site of initiation of transcription and the putative control regions. There is no evident relationship between the localization of intervening sequences in the gene and functional/structural domains of the protein.

Animals↗