Molecular cloning of mevalonate kinase and regulation of its mRNA levels in rat liver.

Tanaka, Richard D.; Lee, Lynn Y.; Schafer, Beverly L.; Kratunis, Valerie J.; Mohler, William A.; Robinson, Gordon W.; Mosley, Stephen T.

doi:10.1073/pnas.87.8.2872

Cited by 68 publications

(47 citation statements)

References 30 publications

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“…For example, a number of other enzymes involved in cholesterol biosynthesis are regulated by sterols. These enzymes include mevalonate kinase (39), farnesyl-pyrophosphate synthase (9), and squalene synthase (13). If regulation of these enzymes is defective in SRD-1, SRD-2, and SRD-6 cells, then it is likely that these enzymes are regulated by the same mechanism that controls HMG-CoA reductase, HMG-CoA synthase, and the LDL receptor.…”

Section: Resultsmentioning

confidence: 99%

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Evans¹,

Metherall²

1993

Mol. Cell. Biol.

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Cholesterol biosynthesis and uptake are controlled by a classic end product-feedback mechanism whereby elevated cellular sterol levels suppress transcription of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein receptor. The 5'-flanking region of each gene contains a common cis-acting element, designated the sterol regulatory element (SRE) cells is limited to transcriptional regulation, since posttranscriptional mechanisms of sterol-mediated regulation were intact: the cells retained the ability to posttranscriptionally suppress HMG-CoA reductase activity and to stimulate acyl-CoA:cholesterol acyltransferase activity. These results suggest that SRD-6 cells lack a factor required for SRE-dependent transcriptional activation. We contrast these cells with a previously isolated oxysterol-resistant cell line (SRD-2) that lacks a factor required for SRE-dependent transcriptional suppression and propose a model for the role of these genetically defined factors in sterol-mediated transcriptional regulation.Mammalian cells demonstrate exquisite control over the level of free cholesterol within the cell (reviewed in reference 17). This control is achieved through the concerted action of a number of mechanisms, including the coordinate transcriptional suppression of the genes encoding 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase, HMG-CoA reductase, and the low-density lipoprotein (LDL) receptor. HMG-CoA synthase and HMG-CoA reductase are the first two committed steps in the pathway of cholesterol biosynthesis, and transcriptional suppression of these genes decreases the rate of cholesterol synthesis. The LDL receptor mediates endocytosis of cholesterol-rich lipoprotein particles such as LDL, and transcriptional suppression of the LDL receptor results in a decreased rate of cholesterol uptake. Transcriptional suppression of these three genes appears to be mediated through a common cis-acting sequence, termed the sterol regulatory element (SRE), that resides in the 5'-flanking region of each gene. A protein that interacts with the SRE of the LDL receptor promoter has recently been identified and purified (1,40 levels rise, the rate of degradation of HMG-CoA reductase is enhanced. This increased degradation requires the membrane-spanning domain of the protein, which anchors it to the endoplasmic reticulum (14). This increased degradation results in decreased HMG-CoA reductase activity and a consequent decrease in the rate of cholesterol synthesis. Sterols also inhibit translation of HMG-CoA reductase mRNA (28), which further decreases the rate of cholesterol synthesis. In addition, sterols stimulate acyl-CoA:cholesterol acyltransferase (ACAT) activity by a mechanism that does not require new protein synthesis (4, 16). ACAT resides in the endoplasmic reticulum and catalyzes the transfer of long-chain fatty acyl residues from acyl-CoA to the 3-hydroxyl group of cholesterol to form cholesteryl esters. While free cholesterol can be deleter...

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Section: Resultsmentioning

confidence: 99%

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Evans¹,

Metherall²

1993

Mol. Cell. Biol.

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“…The aminoterminal analysis was performed with purified protein from three separate purifications, and they repeatedly yielded the same sequence data. The homology search revealed the LHR mRNA-binding protein identity to be rat mevalonate kinase (accession number Q03426) (32).…”

Section: Purification Of Lrbp From Rat Ovary-mentioning

confidence: 99%

Isolation and Characterization of a Novel trans-Factor for Luteinizing Hormone Receptor mRNA from Ovary

Nair

Menon

2004

Journal of Biological Chemistry

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Post-transcriptional mechanisms play a major role in regulating luteinizing hormone (LH) receptor mRNA expression in the ovary. An ovarian cytosolic protein that we have identified in rats and humans, which binds to a polypyrimidine-rich bipartitate sequence in the coding region of LHR mRNA, acts as a trans-acting factor in this process. In the present study, we isolated and characterized this LH receptor mRNA-binding protein (LRBP) from rat ovary. LRBP was purified to homogeneity by cation exchange chromatography followed by Northwestern analysis and subsequent elution of the single protein band from SDS-polyacrylamide gel. Purified LRBP was subjected to N-terminal microsequencing followed by homology search, which revealed its identity as mevalonate kinase. Purified rat mevalonate kinase antibody recognized the gel-purified LRBP on Western blots performed with one-and two-dimensional SDSpolyacrylamide gels. When recombinant mevalonate kinase produced in human embryonic kidney cells ( The interaction of luteinizing hormone (LH) 1 with its cell surface receptors controls reproductive functions including steroidogenesis in the gonad (1). In the ovary, luteinizing hormone receptor (LHR), a member of G s -protein coupled receptors, regulates ovarian function mainly through increased production of cAMP (2-4). The cell surface expression of LHR varies during different stages of the ovarian cycle. Its expression in granulosa cells and luteal cells is greatly decreased by an endogenous preovulatory LH surge or by the administration of a pharmacological dose of human chorionic gonadotropin (hCG), a placental counterpart of LH (5-8). We have shown that the decline in cell surface LHR expression seen after hCG administration is paralleled by a specific loss of all four LHR mRNA transcripts (6.7, 4.4, 2.6, and 1.8 kb) in the ovary (9). Furthermore, the loss of LHR mRNA does not result from decreased transcription but occurs post-transcriptionally with a 3-fold decrease in half-life (8).Regulation of mRNA turnover is one of the major control mechanisms of gene expression in all organisms. mRNA halflives are influenced by the interaction of various cytoplasmic proteins (trans-acting factors) with regulatory regions (cis-acting elements) in the mRNA, forming ribonucleoprotein (RNP) complexes (10). The formation and disruption of RNP complexes in response to various cellular stimuli mainly controls the turnover of cytoplasmic mRNA. Studies have indicated the presence of cis-acting regulatory elements in the 5Ј-untranslated region, coding region, and 3Ј-untranslated region of mRNA (10). A number of cytoplasmic trans-acting factors, some of which shuttle between the nucleus and cytoplasm, have been identified as mRNA-stabilizing, destabilizing, or translational repressor proteins (11-16). c-Fos, c-Myc, tropoelastin, thymidylate synthase, and dihydrofolate reductase are some of the mRNAs containing regulatory elements in the coding region for trans-acting factors (17-24).We have identified a LHR mRNA-binding protein in rat and hu...

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“…Inspection of mevalonate kinase's amino acid sequence does not suggest that substrate ATP binding relies on well established consensus sequences such as Walker A or Walker B motifs. However, two distinct glycine-rich stretches of amino acid sequence have been proposed as potential ATP-binding regions (8,9), although no direct evidence that tests these hypotheses or discriminates between the two candidate sequences has appeared.…”

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confidence: 99%

Investigation of Invariant Serine/Threonine Residues in Mevalonate Kinase

Cho

Rios

Kim

et al. 2001

Journal of Biological Chemistry

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Mevalonate kinase serine/threonine residues have been implicated in substrate binding and inherited metabolic disease. Alignment of >20 mevalonate kinase sequences indicates that Ser-145, Ser-146, Ser-201, and Thr-243 are the only invariant residues with alcohol side chains. These residues have been individually mutated to alanine. Structural integrity of the mutants has been demonstrated by binding studies using fluorescent and spin-labeled ATP analogs. Kinetic characterization of the mutants indicates only modest changes in K m(ATP) . K m for mevalonate increases by Ϸ20-fold for S146A, Ϸ40-fold for T243A, and 100-fold for S201A. V max changes for S145A, S201A, and T243A are <3-fold. Thus, the 65-fold activity decrease associated with the inherited human T243I mutation seems attributable to the nonconservative substitution rather than any critical catalytic function. V max for S146A is diminished by 4000-fold. In terms of V/K MVA , this substitution produces a 10 5 -fold effect, suggesting an active site location and catalytic role for Ser-146. The large k cat effect suggests that Ser-146 productively orients ATP during catalysis. K D(Mg-ATP) increases by almost 40-fold for S146A, indicating a specific role for Ser-146 in liganding Mg 2؉ -ATP. Instead of mapping within a proposed C-terminal ATP binding motif, Ser-146 is situated in a centrally located motif, which characterizes the galactokinase/homoserine kinase/ mevalonate kinase/phosphomevalonate kinase protein family. These observations represent the first functional demonstration that this region is part of the active site in these related phosphotransferases.Isoprenoid biosynthesis is accomplished by diverse pathways that use either acetyl-CoA (1) or glyceraldehyde 3-phosphate and pyruvate (2) as starting materials. Mevalonate kinase (E.C. 2.7.1.36) represents a distinctive component of the former pathway, which functions in eukaryotes, archaebacteria, and some eubacteria. In the mevalonate-mediated pathway for isoprenoid production, attention has long been focused on HMGCoA 1 reductase, which catalyzes a highly regulated step. The diversity of species in which mevalonate kinase functions is reflected in the high degree of heterology that is apparent upon comparison of deduced sequences for this enzyme. Only 5% of the amino acids that encode the human enzyme are invariant. Included in this select group are the residues (Lys-13, 2 Glu-193, Asp-204) that our laboratory has implicated previously (6, 7) in various active site functions. Inspection of mevalonate kinase's amino acid sequence does not suggest that substrate ATP binding relies on well established consensus sequences such as Walker A or Walker B motifs. However, two distinct glycine-rich stretches of amino acid sequence have been proposed as potential ATP-binding regions (8, 9), although no direct evidence that tests these hypotheses or discriminates between the two candidate sequences has appeared.For phosphotransferase enzymes, there are numerous examples of serines or threonines that map to the...

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Molecular cloning of mevalonate kinase and regulation of its mRNA levels in rat liver.

Cited by 68 publications

References 30 publications

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Loss of transcriptional activation of three sterol-regulated genes in mutant hamster cells.

Isolation and Characterization of a Novel trans-Factor for Luteinizing Hormone Receptor mRNA from Ovary

Investigation of Invariant Serine/Threonine Residues in Mevalonate Kinase

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