Ripening-related polygalacturonase cDNA from avocado.
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Amino Acid Sequence↗
Biomedical subjects
S Y Kutsunai
Publications and source records attributed to S Y Kutsunai.
Molecular cloning and promoter analysis of the rat liver farnesyl diphosphate synthase gene.
The isolation and characterization of the rat genomic clone encoding the cholesterogenic enzyme farnesyl diphosphate (FPP) synthase is reported. The gene is localized on a 15-kilobase (kb) genomic fragment, spans approximately 12 kb and contains eight exons. Sequences containing from 3.9 kb to 132 base pairs (bp) of the putative promoter were joined to the coding region of the bacterial reporter gene chloramphenicol acetyltransferase (CAT). The CAT activities or CAT mRNA levels of the hybrid genes were determined following either transient transfections into human hepatoma HepG2 cells or stable transfections into Chinese hamster ovary cells. The transient transfections identified a 319-bp fragment that was required for a 4-fold induction in the absence of sterols. Sequence analysis of this region showed it contained five potential copies of the sterol regulatory element (SRE-1) (Smith, J.R., Osborne, T.F., Brown, M.S., Goldstein, J.L., and Gil, G. (1988) J. Biol. Chem. 263, 18480-18487) previously identified in the promoters of the 3-hydroxy-3-methyl-coenzyme A (HMG-CoA) reductase, HMG-CoA synthase, and low density lipoprotein receptor genes. Further mutational and deletion analysis of the FPP synthase promoter-CAT constructs followed by stable transfection and primer extension of the CAT mRNA levels indicated that these potential SRE-1 regulatory elements were not involved in the sterol-mediated transcriptional regulation of the gene. Our analyses have identified a 115-bp region that is required for the transcriptional induction of FPP synthase in the absence of sterols. These results suggest that the FPP synthase gene may be regulated at the transcriptional level by a different mechanism than other sterol regulated genes.
Alkyl and Aryl Transferases↗
COQ2 is a candidate for the structural gene encoding para-hydroxybenzoate:polyprenyltransferase.
Coenzyme Q functions as a lipid-soluble electron carrier in eukaryotes. In Saccharomyces cerevisiae, the enzymes responsible for the assembly of the polyisoprenoid side chain and subsequent transfer to para-hydroxybenzoate (PHB) are encoded by the nuclear genes COQ1 and COQ2, respectively. Yeast mutants defective in coenzyme Q biosynthesis are respiratory defective and provide a useful tool to study this non-sterol branch of the isoprenoid biosynthetic pathway. We isolated a 5.5-kilobase genomic DNA fragment that was able to functionally complement a coq2 strain. Additional complementation analyses located the COQ2 gene within a 2.1-kilobase HindIII-BglII restriction fragment. Sequence analyses revealed the presence of a 1,116-base pair open reading frame coding for a predicted protein of 372 amino acids and a molecular mass of 41,001 daltons. The amino acid sequence exhibits a typical amino-terminal mitochondrial leader sequence and six potential membrane-spanning domains. Primer extension and Northern analyses indicate the gene is transcriptionally active. Transformation of a coq2 strain with the 2.1-kilobase HindIII-BglII genomic restriction fragment on a multicopy plasmid restores PHB:polyprenyltransferase activity to wild-type levels. Disruption of the chromosomal COQ2 gene indicates the gene is not essential for viability, yet is required for PHB:polyprenyltransferase activity and respiratory function. In addition, the deduced amino acid sequence of PHB:polyprenyltransferase contains a putative allylic polyprenyl diphosphate-binding site. The presence of this aspartate-rich domain in a number of functionally distinct proteins which utilize polyprenyl diphosphate substrates is reported.
Alkyl and Aryl Transferases↗
Isolation and sequence of the human farnesyl pyrophosphate synthetase cDNA. Coordinate regulation of the mRNAs for farnesyl pyrophosphate synthetase, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and 3-hydroxy-3-methylglutaryl coenzyme A synthase by phorbol ester.
We report the isolation and nucleotide sequence of the human farnesyl pyrophosphate synthetase cDNA, an enzyme in the cholesterogenic pathway. Partial cDNAs for the human farnesyl pyrophosphate synthetase were isolated by screening human hepatoma (HepG2) and placental cDNA libraries with the rat liver cDNA for farnesyl pyrophosphate synthetase as a probe. Anchored polymerase chain reaction was used to isolate the 5'-end of the cDNA. The nucleotide sequence of the human farnesyl pyrophosphate synthetase cDNA has high identity (86%) to the rat liver cDNA. Treatment of the human monocytic leukemia cell line THP-1 with phorbol esters led to 2--7-fold increases in mRNA concentrations for the three cholesterogenic enzymes, farnesyl pyrophosphate synthetase, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and HMG-CoA synthase within 5 h. Immunoprecipitation of radiolabeled cells demonstrated that there was a corresponding increase in the rate of synthesis of all three proteins. The addition of cycloheximide to cells also led to increases in the mRNA concentrations of the three enzymes. Treatment of cells with phorbol esters and cycloheximide resulted in superinduction of all three mRNAs; HMG-CoA synthase mRNA levels increased 35-fold, farnesyl pyrophosphate synthetase 17-fold, and HMG-CoA reductase 16-fold 5 h after treatment. The mRNA levels returned to pretreatment levels by 20 h. Cells were also preincubated in the presence of a lipoprotein-deficient fraction of serum plus mevinolin to induce the levels of the three mRNAs. Addition of phorbol esters and cycloheximide to these derepressed cells led to further increases in the mRNA levels for all three enzymes. These results are consistent with the hypothesis that THP-1 cells contain a short-lived negative transcription factor which regulates transcription of the FPP synthetase, HMG-CoA reductase, and HMG-CoA synthase genes. Phorbol esters also regulate these same genes, presumably by modifying a common negative transcription factor and/or by inducing a positive transcription factor(s).
Amino Acid Sequence↗
Testis-specific transcription initiation sites of rat farnesyl pyrophosphate synthetase mRNA.
A variety of rat tissues were screened at low stringency with a rat farnesyl pyrophosphate (FPP) synthetase cDNA. In testis, an FPP synthetase-related RNA was detected that was larger than the liver FPP synthetase mRNA and was present at very high levels comparable with liver FPP synthetase RNA levels obtained from rats fed diets supplemented with cholestyramine and mevinolin. Sequence analysis of testis cDNA clones, together with primer extension and S1 nuclease experiments, indicated that testis FPP synthetase transcripts contain an extended 5' untranslated region. The 5' extension contained one or two out-of-frame upstream ATGs, depending on the site of transcription initiation. Protein in vitro translation studies indicated that the extended 5' untranslated region may play a role in regulating the translation of the FPP synthetase polypeptide in rat testis. Southern blot analysis with a probe containing both testis and liver 5' untranslated sequences provided evidence that both liver and testis transcripts derive from the same gene. The data suggest that an upstream testis-specific promoter results in the abundant production of FPP synthetase transcripts that are translated at low efficiency; another promoter functions in liver and other somatic tissues and directs the regulated synthesis of shorter discrete transcripts.
Amino Acid Sequence↗