Browsing by Author "BULL, P"

Now showing 1 - 14 of 14
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    CHEMICAL MODIFICATION OF LYSYL AND CYSTEINYL RESIDUES OF YEAST RNA POLYMERASE-I
    (1981) BULL, P; ZALDIVAR, J; WYNEKEN, U; VENEGAS, A; VALENZUELA, P
    The active site of yeast RNA polymerase I was studied using pyridoxal 5''-phosphate, p-chloromercuribenzoate and 5,5''-dithiobis (2-nitrobenzoate) as modifying agents. The enzyme was rapidly inactivated by pyridoxal 5''-phosphate, by formation of a Schiff base between the aldehyde group and lysine amino groups of the enzyme, located in the largest subunit. Out of 45 SH groups, 2 are required for enzyme activity. Since they were partially protected by substrates and DNA, they may be at the active site. A hypothetical model of catalysis is proposed based on the results presented.
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    ELECTRON-MICROSCOPY MAPPING OF ESCHERICHIA-COLI RNA POLYMERASE-BINDING SITES ON PLASMIDS FROM THERMOPHILIC BACTERIA
    (1984) GONZALEZ, B; VASQUEZ, C; BULL, P; VICUNA, R
    The binding sites of E. coli RNA polymerase to plasmid DNA from extremely thermophilic bacteria were mapped by EM. Templates used in these studies included plasmids pTF62 (from Thermus flavus AT62) and pTT8 (from T. thermophilus HB8) and hybrid molecules constructed by ligation of these plasmids to pBR322. Although the affinity of the enzyme for heterologous DNA was .apprx. 1/3 of that for pBR322, it was possible to localize preferred binding sites on pTF62 and pTT8. Six binding sites were identified in pTT8, mapping close to 7, 28, 47, 61, 65 and 81 map units (1 unit = 1% of the length of the DNA). Seven such regions located at 3, 27, 48, 60, 67, 81 and 86 map units were found in pTF62. RNA polymerase binding sites found in pBR322 coincided with promoters identified previously by EM analysis of transcriptional complexes prepared in vitro. Evidently, E. coli RNA polymerase binds preferentially to specific sequences in plasmids from thermophilic bacteria, suggesting possible promoter locations in these plasmids.
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    ISOLATION AND STRUCTURE OF A YEAST INITIATOR TRANSFER RNA-MET GENE
    (1982) VENEGAS, A; GONZALEZ, E; BULL, P; VALENZUELA, P
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    MUTAGENIC SUBSTANCES IN RED AND WHITE WINE IN CHILE, A HIGH-RISK AREA FOR GASTRIC-CANCER
    (1987) BULL, P; YANEZ, L; NERVI, F
    Chilean home-made and commercial wines were analyzed for the presence of mutagenic substances using the Salmonella mutagenicity test with preincubation. Strains TA98 and TA100 were used in the absence and in the presence of S9 mix. 90% of red wines from a total of 30 samples and 54% of white wines from a total of 22 were found to be mutagenic. In all cases, S9 mix did not affect the mutagenicity of the samples. At least in one case, more than one mutagen was present, since the mutagenicity with TA98 could be selectively inactivated without affecting that with TA100. This study supports the hypothesis that wine consumption may be an important risk factor for upper gastrointestinal cancer, particularly for adenocarcinoma of the stomach, which is highly prevalent in Chile.
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    NOVEL GENETIC-MARKERS OF RHEUMATOID-ARTHRITIS IN CHILEAN PATIENTS, BY DR SEROTYPING AND RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSIS
    (1992) GONZALEZ, A; NICOVANI, S; MASSARDO, L; BULL, P; RODRIGUEZ, L; JACOBELLI, S
    Objective. The analysis of genetic markers of rheumatoid arthritis (RA) in a population in which the DR4 serotype is not strongly associated with the disease.
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    RELB, A NEW REL FAMILY TRANSCRIPTION ACTIVATOR THAT CAN INTERACT WITH P50-NF-KAPPA-B
    (1992) RYSECK, RP; BULL, P; TAKAMIYA, M; BOURS, V; SIEBENLIST, U; DOBRZANSKI, P; BRAVO, R
    We have identified a serum-inducible gene, relB, which encodes a protein of 558 amino acids containing a region with high similarity to c-Rel and other members of the Rel family. Transcriptional activation analysis of GAL4-RelB fusion proteins in yeast cells reveals that RelB contains in its C-terminal 180 amino acids a transcriptional activation domain. The N-terminal part including the region of similarity with the Rel family shows no detectable transcriptional activity. RelB does not bind with high affinity to NF-kappa-B sites, but heterodimers between RelB and p50-NF-kappa-B do bind to different NF-kappa-B-binding sites with a similar affinity to that shown by p50-NF-kappa-B homodimers. However, RelB/p50-NF-kappa-B heterodimers, in contrast to p50-NF-kappa-B homodimers, transactivate transcription of a promoter containing a kappa-B-binding site.
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    STRUCTURE OF THE EUKARYOTIC GENOME - A UNIQUE PSEUDOGENE LACKING INTRONS AND POLY-A TAIL AS A MEMBER OF THE HUMAN BETA-TUBULIN GENE FAMILY
    (1982) PICHUANTES, S; MEDINA, A; BELL, G; GOMEZ, I; VALENZUELA, P; BULL, P; VENEGAS, A
    From a human gene bank constructed in the vector phage Charon 4A, 14 clones carrying complementary sequences to .alpha. and .beta. tubulin chicken c[complementary]DNA were isolated. A preliminary structural analysis of some of the .beta. clones, based on restriction digests followed by Southern hybridization, allowed us to select clone .beta.9 as the one containing a functional gene. After further analysis this clone was proved to contain a pseudogene. The coding sequence is altered by 4 stop codons, 6 short delections and 2 1-base insertions. These changes prevent any correct translation. The pseudogene seems to preserve some vestigial control regions and does not contain introns. No in vitro RNA synthesis directed by this clone was detected.
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    STRUCTURE OF YEAST RNA-POLYMERASES DETERMINED BY ELECTRON-MICROSCOPY
    (1982) BULL, P; GARRIDO, J
    Methods were developed for the examination of yeast RNA polymerases I, II and III by EM. The size and shape of a eucaryotic RNA polymerase was established for the 1st time. The enzymes are roughly spherical in shape and compact in appearance. Their measured molecular diameters are 12.7 .+-. 0.4 and 11.0 .+-. 1.4 (SD) nm for polymerase I, 12.7 .+-. 1.1 and 12.2 .+-. 1.0 (SD) nm for polymerase II and 13.6 .+-. 0.6 and 11.5 .+-. 1.3 (SD) nm for polymerase III.
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    SUB-CELLULAR DISTRIBUTION OF CHOLESTEROL ESTER HYDROLASE IN HUMAN-LIVER
    (1981) DELPOZO, R; BRONFMAN, M; BULL, P; NERVI, F
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    SUBUNITS OF YEAST RNA POLYMERASE-I INVOLVED IN INTERACTIONS WITH DNA AND NUCLEOTIDES
    (1978) VALENZUELA, P; BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, J
    Reaction of yeast [Saccharomyces cerevisiae] RNA polymerase I with pyridoxal 5''-phosphate and sodium borohydride under conditions which inactivate the enzyme results in the specific binding of pyridoxal 5''-phosphate to subunits of 185,000, 137,000, 48,000 and 36,000 daltons. Nucleotides, which protect the enzyme from inactivation specifically inhibit the binding of pyridoxal 5''-phosphate to subunits of 185,000 and 137,000 daltons. DNA which also protects the enzyme from inactivation by pyridoxal 5''-phosphate prevents the binding of the reagent to the 4 polypeptides. These results suggest that subunits of 185,000 and 137,000 are involved in interactions with both nucleotides and DNA presumably of the type leading to initiation and/or polymerization and that subunits of 48,000 and 36,000 daltons also bind to DNA but this interaction is not strictly required for polymerase activity.
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    THE PH-DEPENDENCE OF RAT-LIVER RNA POLYMERASE-I AND POLYMERASE-II
    (1980) BULL, P; MARTIAL, J; TELLEZ, R; VENEGAS, A; VALENZUELA, P
    The effect of pH on the stability and activity of rat liver RNA polymerases I (A) and II (B) was studied. Both enzymes are irreversibly inactivated in buffer solutions below pH 5.0. Km values of the 2 enzymes are constant between pH 6.5 and 8.7, but a 2- to 3-fold increase is observed between pH 8.7 and 9.7. The Vmax vs. pH profiles are bell-shaped curves indicating the participation of 2 ionizing groups with apparent pKa values of 6.5 and 9.8 for enzyme I and 6.7 and 9.9 for enzyme II. Both enzymes are inactivated by photooxidation in the presence of Rose Bengal. The above pKa corresponds to the imidazole of a histidine residue and an amino group of a lysine residue.
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    THE YEAST TRANSFER RNAPHE GENE FAMILY - STRUCTURES AND TRANSCRIPTIONAL ACTIVITIES REVEAL MEMBER DIFFERENCES NOT EXPLAINED BY INTRAGENIC PROMOTERS
    (1987) BULL, P; THORIKAY, M; MOENNE, A; WILKENS, M; SANCHEZ, H; VALENZUELA, P; VENEGAS, A