Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The genes norCBQD that encode the bc-type nitric oxide reductase from Bradyrhizobium japonicum USDA110 have been isolated and characterized. norC and norB encode the cytochrome c-containing subunit II and cytochrome b-containing subunit I of nitric oxide reductase, respectively. norQ encodes a protein with an ATP/GTP-binding motif, and the predicted norD gene product shows similarity with NorD from other denitrifiers. Mutational analysis indicates that the two structural norC and norB genes are required for microaerobic growth under nitrate-respiring conditions. A mutant strain lacking a functional norC gene also lacked the 16 kDa c-type cytochrome that is normally detectable by haem-staining of proteins from membranes of microaerobically grown wild-type cells. Expression of a transcriptional fusion of the nor promoter region to the reporter gene lacZ (P(norC)-lacZ) was not detected in aerobically grown cells of USDA110, but the fusion was induced threefold when the cells were cultured under microaerobic conditions (1% O(2)) with either nitrite or nitric oxide, and about 18-fold when nitrate was the N oxide present in the medium. The P(norC)-lacZ fusion was not expressed in the B. japonicum fixK(2) mutant strain 9043, but complementation of the mutant with the fixK(2) gene restored beta-galactosidase activity to levels similar to those found in the parental strain. The promoter region of the norCBQD genes has been characterized by primer extension. A major transcript initiates 45.5 bp downstream of the centre of a putative binding site for the transcription factor FixK(2).
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PMID:Characterization of the norCBQD genes, encoding nitric oxide reductase, in the nitrogen fixing bacterium Bradyrhizobium japonicum. 1242 46

CTP synthase is encoded by the pyrG gene and catalyzes the conversion of UTP to CTP. A Lactococcus lactis pyrG mutant with a cytidine requirement was constructed, in which beta-galactosidase activity in a pyrG-lacLM transcriptional fusion was used to monitor gene expression of pyrG. A 10-fold decrease in the CTP pool induced by cytidine limitation was found to immediately increase expression of the L. lactis pyrG gene. The final level of expression of pyrG is 37-fold higher than the uninduced level. CTP limitation has pronounced effects on central cellular metabolism, and both RNA and protein syntheses are inhibited. Expression of pyrG responds only to the cellular level of CTP, since expression of pyrG has no correlation to alterations in UTP, GTP, and ATP pool sizes. In the untranslated pyrG leader sequence a potential terminator structure can be identified, and this structure is required for regulation of the pyrG gene. It is possible to fold the pyrG leader in an alternative structure that would prevent the formation of the terminator. We suggest a model for pyrG regulation in L. lactis, and probably in other gram-positive bacteria as well, in which pyrG expression is directly dependent on the CTP concentration through an attenuator mechanism. At normal CTP concentrations a terminator is preferentially formed in the pyrG leader, thereby reducing expression of CTP synthase. At low CTP concentrations the RNA polymerase pauses at a stretch of C residues in the pyrG leader, thereby allowing an antiterminator to form and transcription to proceed. This model therefore does not include any trans-acting protein for sensing the CTP concentration as previously proposed for Bacillus subtilis.
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PMID:CTP limitation increases expression of CTP synthase in Lactococcus lactis. 1459 29

Human lens epithelium-derived growth factor (LEDGF)/p75 protein forms a specific nuclear complex with human immunodeficiency virus type 1 (HIV-1) integrase and is essential for nuclear localization and chromosomal association of the viral protein. We now studied nuclear import of LEDGF/p75 in live and semipermeabilized cells. We show that nuclear import of LEDGF/p75 is GTP-, Ran-, importin-alpha/beta-, and energy-dependent and that the protein competes with the canonical SV40 large T antigen nuclear localization signal (NLS) for nuclear import receptors. We identified the NLS of LEDGF/p75 through deletion analysis and site-directed mutagenesis. The LEDGF/p75 NLS, 148GRKRKAEKQ156, belongs to the canonical SV40-like family. Fusion of this short peptide to the amino terminus of Escherichia coli beta-galactosidase rendered the fusion protein nuclear, confirming that the LEDGF/p75 NLS is transferable. Moreover, a single amino acid change in the NLS was sufficient to exclude the mutant LEDGF/p75 protein from the nucleus and abolish nuclear import of HIV-1 integrase.
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PMID:Identification and characterization of a functional nuclear localization signal in the HIV-1 integrase interactor LEDGF/p75. 1516 64

Cdc42 is a member of the Rho GTPase family known to regulate cell actin cytoskeleton organization, polarity, and growth, but its function in mammalian organismal physiology remains unclear. We found that natural aging of WT mice is marked with increased Cdc42 activity in various tissues. Among the negative regulators of Cdc42, gene targeting of Cdc42 GTPase-activating protein (Cdc42GAP) results in constitutively elevated Cdc42-GTP level in diverse tissues of adult mice; significantly shortened life span of the animals; and multiple premature aging-like phenotypes, including a reduction in body mass, a loss of subdermal adipose tissue, severe lordokyphosis, muscle atrophy, osteoporosis, and reduction of reepithelialization ability in wound-healing. Cdc42GAP-/- mouse embryonic fibroblasts and/or tissues display reduced population doubling, significantly dampened DNA damage repair activity after DNA-damaging agent treatment, accumulated genomic abnormalities, and induction of p53, p16Ink4a, p21Cip1, and senescence-associated beta-galactosidase expressions. Furthermore, Cdc42 activation is sufficient to promote a premature cellular senescence phenotype that depends on p53. These results suggest a role of Cdc42 activity in regulating mammalian genomic stability and aging-related physiology.
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PMID:Cdc42 GTPase-activating protein deficiency promotes genomic instability and premature aging-like phenotypes. 1722 69

Arginine vasopressin (AVP), a vasoactive peptide hormone that binds to three G-protein coupled receptors (V1R, V2R, and V3R), has long been known to activate V1R and elicit mitogenesis in several cell types, including adrenal glomerulosa cells. However, in the mouse Y1 adrenocortical malignant cell line, AVP triggers not only a canonical mitogenic response but also novel RhoA-GTP-dependent mechanisms which downregulate cyclin D1, irreversibly inhibiting K-ras oncogene-driven proliferation. In Y1 cells, AVP blocks cyclin D1 expression, induces senescence-associated beta-galactosidase (SAbeta-Gal) and inhibits proliferation. However, ectopic expression of cyclin D1 renders Y1 cells resistant to both SAbeta-Gal induction and proliferation inhibition by AVP. In addition, ectopic expression of the dominant negative RhoAN19 mutant blocks RhoA activation, yielding Y1 cell sub-lines which are no longer susceptible to cyclin D1 downregulation, SAbeta-Gal induction, or proliferation inhibition by AVP. Furthermore, inhibiting RhoA with C3 exoenzyme protects Y1 cells from AVP proliferation inhibition and SAbeta-Gal induction. On the other hand, AVP treatment does not activate caspases 3 and 7, and the caspase inhibitor Ac-DEVD-CMK does not protect Y1 cells from proliferation inhibition by AVP, implying that AVP does not trigger apoptosis. These results underline a pivotal survival activity of cyclin D1 that protects K-ras oncogene-dependent malignant cells from senescence.
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PMID:Vasopressin triggers senescence in K-ras transformed cells via RhoA-dependent downregulation of cyclin D1. 1804 63

Fibroblast growth factor 2 (FGF2) is considered to be a bona fide oncogenic factor, although results from our group and others call this into question. Here, we report that exogenous recombinant FGF2 irreversibly inhibits proliferation by inducing senescence in Ras-dependent malignant mouse cells, but not in immortalized nontumorigenic cell lines. We report the following findings in K-Ras-dependent malignant Y1 adrenocortical cells and H-Ras V12-transformed BALB-3T3 fibroblasts: (a) FGF2 inhibits clonal growth and tumor onset in nude and immunocompetent BALB/c mice, (b) FGF2 irreversibly blocks the cell cycle, and (c) FGF2 induces the senescence-associated beta-galactosidase with no accompanying signs of apoptosis or necrosis. The tyrosine kinase inhibitor PD173074 completely protected malignant cells from FGF2. In Y1 adrenal cells, reducing the constitutively high levels of K-Ras-GTP using the dominant-negative RasN17 mutant made cells resistant to FGF2 cytotoxicity. In addition, transfection of the dominant-negative RhoA-N19 into either Y1 or 3T3-B61 malignant cell lines yielded stable clonal transfectants that were unable to activate RhoA and were resistant to the FGF2 stress response. We conclude that in Ras-dependent malignant cells, FGF2 interacts with its cognate receptors to trigger a senescence-like process involving RhoA-GTP. Surprisingly, attempts to select FGF2-resistant cells from the Y1 and 3T3-B61 cell lines yielded only rare clones that (a) had lost the overexpressed ras oncogene, (b) were dependent on FGF2 for proliferation, and (c) were poorly tumorigenic. Thus, FGF2 exerted a strong negative selection that Ras-dependent malignant cells could rarely overcome.
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PMID:Fibroblast growth factor 2 restrains Ras-driven proliferation of malignant cells by triggering RhoA-mediated senescence. 1867 45

Polo-like kinase 1 plays an essential role in mitosis and cytokinesis. Expression and nuclear localization of Plk1 during the S phase are necessary for its functions. Although it was reported that a bipartite nuclear localization signal located at the N-terminal kinase domain is required for nuclear import of Plk1, Plk1 carrying mutations in the polo box I of the polo box domain exhibited increased cytoplasmic accumulation. We further showed that the polo box domain was able to confer nuclear import of beta-galactosidase in vivo and GST-EGFP in vitro. The import carriers transportin and importin alpha were found to interact with the polo box domain directly in a Ran-GTP sensitive manner. These results indicate the presence of a nuclear localization signal in the polo box domain. A 38 amino acid sequence with the function of nuclear localization signal was identified to interact with transportin. Our findings demonstrated that a transportin-dependent nuclear localization signal is present in the polo box domain of Plk1, possibly required for efficient nuclear import. Showing little similarity to the M9 sequence, the 38 amino acid sequence identified here likely represents a novel nuclear localization signal.
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PMID:Identification of a nuclear localization signal in the polo box domain of Plk1. 1963 97


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