Browsing by Author "VENEGAS, A"
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- ItemCHEMICAL MODIFICATION OF LYSYL AND CYSTEINYL RESIDUES OF YEAST RNA POLYMERASE-I(1981) BULL, P; ZALDIVAR, J; WYNEKEN, U; VENEGAS, A; VALENZUELA, PThe 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.
- ItemCONDITIONS AFFECTING DNA CLEAVAGE BY TTHI AT A TTHI ENDONUCLEASE-DAM METHYLASE OVERLAPPING SEQUENCE(1981) VENEGAS, A; MOTLES, M; VASQUEZ, C; VICUNA, R
- ItemINACTIVATION OF ESCHERICHIA-COLI RNA-POLYMERASE BY PYRIDOXAL 5'-PHOSPHATE - IDENTIFICATION OF A LOW PKA LYSINE AS MODIFIED RESIDUE(1975) BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, J; VALENZUELA, P
- ItemISOLATION AND STRUCTURE OF A YEAST INITIATOR TRANSFER RNA-MET GENE(1982) VENEGAS, A; GONZALEZ, E; BULL, P; VALENZUELA, P
- ItemMOLECULAR-CLONING AND EXPRESSION IN ESCHERICHIA-COLI OF A SALMONELLA-TYPHI PORIN GENE(1988) ZAROR, I; GOMEZ, I; CASTILLO, G; YUDELEVICH, A; VENEGAS, A
- ItemNUCLEOTIDE-SEQUENCE OF A YEAST TRANSFER RNA3A(ARG) GENE AND ITS TRANSCRIPTION IN A HOMOLOGOUS INVITRO SYSTEM(1984) VILLANUEVA, J; BULL, P; VALENZUELA, P; VENEGAS, A
- ItemRAPID PROCEDURE FOR PURIFYING A RESTRICTION ENDONUCLEASE FROM THERMUS-THERMOPHILUS (TTH I)(1980) VENEGAS, A; VICUNA, R; ALONSO, A; VALDES, F; YUDELEVICH, A
- ItemROTAVIRUS DETECTION BY DOT BLOT HYBRIDIZATION ASSAY USING A NONRADIOACTIVE SYNTHETIC OLIGODEOXYNUCLEOTIDE PROBE(1992) FERNANDEZ, J; SANDINO, A; YUDELEVICH, A; AVENDANO, LF; VENEGAS, A; HINRICHSEN, V; SPENCER, EA synthetic oligodeoxynucleotide of 40 nucleotides corresponding to nucleotides 33-72 of the gene coding for the viral protein VP7 of rotavirus. was used as a nucleic acid probe to develop a non-radioactive hybridization method for rotavirus detection. The probe was labelled at the 3' end with biotin-7-dATP. The sensitivity and specificity of the dot blot hybridization assay for rotavirus detection was evaluated with 303 stool specimens. The results indicate that the hybridization assay has a higher sensitivity than both PAGE and EIA. Among the rotavirus strains tested 37 different electropherotypes were found. The results suggest that rotavirus diagnosis by dot hybridization using a non-radioactive probe may become routine laboratory procedure because it is simple, highly specific and very sensitive.
- ItemSTRUCTURE 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, AFrom 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.
- ItemSUBUNITS OF YEAST RNA POLYMERASE-I INVOLVED IN INTERACTIONS WITH DNA AND NUCLEOTIDES(1978) VALENZUELA, P; BULL, P; ZALDIVAR, J; VENEGAS, A; MARTIAL, JReaction 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.
- ItemTHE PH-DEPENDENCE OF RAT-LIVER RNA POLYMERASE-I AND POLYMERASE-II(1980) BULL, P; MARTIAL, J; TELLEZ, R; VENEGAS, A; VALENZUELA, PThe 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.
- ItemTHE 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
- ItemYEAST TRANSFER RNA3LEU GENE TRANSCRIBED AND SPLICED IN A HELA-CELL EXTRACT(1981) STANDRING, DN; VENEGAS, A; RUTTER, WJA cloned yeast tRNA3Leu gene containing a 33-base intervening sequence (IVS) is selectively transcribed by a soluble extract from HeLa cells. The 130-nucleotide tRNA3Leu precursor RNA formed is colinear with the gene and contains approximately 4 leader nucleotides and up to 9 trailer nucleotides. The IVS is accurately and efficiently removed by an endogenous HeLa excision-ligase activity to yield the spliced tRNA, the free IVS, and the half-tRNA intermediates. The splicing reaction occurs without prior 5'' and 3'' maturation of the precursor but, with this exception, this pattern of synthesis and subsequent maturation of the tRNA3Leu precursor conforms to the scheme for tRNA biosynthesis deduced for the Xenopus system. The 3 systems utilize similar or identical tRNA3Leu precursors. Results stress the extraordinary conservation of tRNA biosynthesis in eukaryotes and demonstrate that a HeLa extract provides a useful system for investigating this process.