Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.10.2 (focal adhesion kinase)
 44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

IMP dehydrogenase is a rate-limiting enzyme involved in the synthesis of GTP. In mammalian cells it is regulated with respect to growth rate and is the target of numerous therapeutic agents. Mutations in the RNA polymerase II elongation machinery render yeast sensitive to inhibitors of IMP dehydrogenase and defective in inducing transcription of one of the IMP dehydrogenase-encoding genes, IMD2. Here we show that loss of IMD2, but not IMD1, IMD3, or IMD4, conferred upon yeast the same drug sensitivity found in elongation mutants. We tested whether the drug sensitivity of elongation mutants is due to their inability to induce IMD2 by providing them with exogenous copies of the gene. In some elongation mutants, overexpression reversed drug sensitivity and a transcriptional defect. Overexpression in mutants with a more severe phenotype partially suppressed drug sensitivity but was inconsequential in reversing a defect in transcription. These findings suggest that the drug sensitivity of elongation mutants is largely but not solely attributable to defects in the ability to induce IMD2, because transcription is compromised even when IMD2 mRNA levels are adequate. We describe two DNA sequence elements in the promoter of the gene that regulate it. We also found that IMD2 mRNA abundance is coupled to cell growth rate. These findings show that yeast possess a conserved system that gauges nucleotide pools and cell growth rate and responds through a uniquely regulated member of the IMD gene family.
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PMID:Regulation of an IMP dehydrogenase gene and its overexpression in drug-sensitive transcription elongation mutants of yeast. 1144 Oct 18

IMP dehydrogenase (IMPDH) catalyzes the rate-limiting step in the de novo synthesis of GTP. Yeast with mutations in the transcription elongation machinery are sensitive to inhibitors of this enzyme such as 6-azauracil and mycophenolic acid, at least partly because of their inability to transcriptionally induce IMPDH. To understand the molecular basis of this drug-sensitive phenotype, we have dissected the expression and function of a four-gene family in yeast called IMD1 through IMD4. We show here that these family members are distinct, despite a high degree of amino acid identity between the proteins they encode. Extrachromosomal copies of IMD1, IMD3, or IMD4 could not rescue the drug-sensitive phenotype of IMD2 deletants. When overexpressed, IMD3 or IMD4 weakly compensated for deletion of IMD2. IMD1 is transcriptionally silent and bears critical amino acid substitutions compared with IMD2 that destroy its function, offering strong evidence that it is a pseudogene. The simultaneous deletion of all four IMD genes was lethal unless growth media were supplemented with guanine. This suggests that there are no other essential functions of the IMPDH homologs aside from IMP dehydrogenase activity. Although neither IMD3 nor IMD4 could confer drug resistance to cells lacking IMD2, either alone was sufficient to confer guanine prototrophy. The special function of IMD2 was provided by its ability to be transcriptionally induced and the probable intrinsic drug resistance of its enzymatic activity.
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PMID:Functional distinctions between IMP dehydrogenase genes in providing mycophenolate resistance and guanine prototrophy to yeast. 1274 40

IMP dehydrogenase (IMPDH) is the rate-limiting enzyme for de novo GMP synthesis. Its activity is correlated with cell growth, and it is the target of a number of proven and experimental drug therapies including mycophenolic acid (MPA). MPA inhibits the enzyme by trapping a covalent nucleotide-enzyme intermediate. Saccharomyces cerevisiae has four IMPDH genes called IMD1-IMD4. IMD2 is transcriptionally regulated and is the only one that enables yeast to grow in the presence of MPA. We show here that de novo synthesis of the IMD2-encoded protein is strongly induced upon MPA treatment. We also monitor the in vivo formation of a covalent nucleotide-enzyme intermediate for Imd2, Imd3, and Imd4 that accumulates in the presence of MPA. Complete formation of the Imd2 intermediate requires drug concentrations manyfold higher than that required to quantitatively trap the Imd3- or Imd4-nucleotide adducts. Purification of the tagged IMD gene products reveals that the family of polypeptides coassemble to form heteromeric IMPDH complexes, suggesting that they form mixed tetramers. These data demonstrate that S. cerevisiae harbor multiple IMPDH enzymes with varying drug sensitivities and offer an assay to monitor the inhibition of IMPDH in living cells. They also suggest that mixed inhibition profiles may result from heteromeric complexes in cell types that contain multiple IMPDH gene products. The mobility shift assay could serve as a tool for the detection of drug-inactivated IMPDH in the cells of patients receiving MPA therapy.
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PMID:Detection of the mycophenolate-inhibited form of IMP dehydrogenase in vivo. 1529 16

IMP dehydrogenase (IMPDH) is required for the de novo synthesis of guanine nucleotides. While most invertebrates have one IMPDH gene and humans and mice have two, Saccharomyces cerevisiae contains four, IMD1-IMD4. Although Imd2 is 92% identical to Imd3, it is the only S. cerevisiae IMPDH that is resistant to mycophenolic acid in vitro and is the only one of the four that supports drug-resistant growth. Thus, S. cerevisiae is unique in possessing two classes of IMPDH enzymes with very different drug susceptibilities. The mycophenolate-sensitive growth phenotype has become an important genetic tool in yeast, particularly as an indicator for mutations in the transcription elongation machinery. Here we exploit the distinct drug sensitivity of these two closely related IMPDH genes to identify the naturally occurring determinants of drug-resistant growth. Using chimeric IMD2-IMD3 genes in a strain null for IMD genes, we show that one of the 39 amino acid differences between these enzymes is responsible for much of its drug resistance. The IMP dehydrogenase activity of purified chimeric Imd3 containing the Imd2 residue at position 253 was eight-fold more resistant than native Imd3. The reciprocal change in Imd2 resulted in a 23-fold loss of resistance. Hence, acquisition of a hydroxyl side-chain at 523 is sufficient to confer a drug-resistant phenotype upon this organism. We identified the major determinant of the functional distinction between IMD genes in this yeast and suggest that selective pressure on this species forced divergence of one member of this gene family toward drug resistance.
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PMID:Dissection of the molecular basis of mycophenolate resistance in Saccharomyces cerevisiae. 1627 36

IMP dehydrogenase (IMPDH) catalyzes the rate-limiting step in the de novo synthesis of guanine, namely the oxidation of IMP to XMP with a concomitant reduction of NAD+. In Saccharomyces cerevisiae, a family of four closely-related genes, IMD1, IMD2 (also known as PUR5), IMD3, and IMD4, encodes the putative IMPDH. Although IMPDH synthesizes guanine in the cytoplasm, it has also been found in the nucleus, where it associates with nucleic acids in human cells. Here, we further show that IMPDH is recruited to actively transcribed region of genes. A synthetic lethal screen using a deletion strain of Ctk1 kinase, a yeast homolog of mammalian Cdk9/P-TEFb that phosphorylates serine 2 within the RNA polymerase II (RNApII) C-terminal domain (CTD), identified that Imd2 genetically interacts with Ctk1. Consistent with this association, IMPDHs were recruited to elongating RNApII only when serine 2 of the CTD was phosphorylated by Ctk1. Loss of Imd2 had little effect on the association of most elongation factors with RNApII. However, in cells lacking Imd2 or all the essential IMPDHs in the presence of minimal guanine, a defect in the association of Ctk1 with the promoter region was seen. Taken together, our results show that IMPDH is recruited to transcription complex through serine 2 phosphorylation of RNApII CTD and suggest that it may play a role in initiating transcriptional regulation.
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PMID:IMP dehydrogenase is recruited to the transcription complex through serine 2 phosphorylation of RNA polymerase II. 2009 57