Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.23 (beta-galactosidase)
 14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the role of 5'-flanking DNA sequences in regulating the expression of the murine Sparc (osteonectin) gene in parietal endoderm cells and in F9 embryonal carcinoma cells induced to differentiate into parietal endoderm with retinoic acid and cyclic AMP. Varying lengths of flanking sequences extending up to 3.0 kilobase pairs 5' of the transcription initiation site were linked to the bacterial chloramphenicol transacetylase gene in the Bluescript M13- vector. The constructs were tested in transient assays, using a beta-galactosidase plasmid as a transfection control. Sequences between 78 and 169 base pairs upstream of the cap site are the minimum required for cell-type specific promoter activity; this region is dominated by two oligopurine/oligopyrimidine stretches or "GAGA" boxes and is highly conserved between the mouse and bovine genes. Addition of the sequence between -169 and -449, which includes part or all of a third GAGA box, results in increased parietal endoderm specific transcription, up to a maximum of 6.3-fold higher than in undifferentiated F9 cells. Further addition of sequences between -449 and -638 markedly reduces promoter activity in both cell types but parietal endoderm-specific activity is restored in constructs containing 2.2 and 3.0 kilobase pairs of flanking DNA. In addition, we have identified sequences related to the consensus sequence for steroid response elements, one of which is able to confer progesterone-enhanced transcription when tested with a heterologous promoter in steroid responsive cells. These results suggest that negative and positive elements normally interact to regulate the temporal and tissue-specific patterns of Sparc gene transcription seen in vivo.
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PMID:Evidence for positive and negative regulatory elements in the 5'-flanking sequence of the mouse sparc (osteonectin) gene. 274 36

The extracellular matrix-associated protein, SPARC (osteonectin [Secreted Protein Acidic and Rich in Cysteine]), modulates cell adhesion and induces a change in cell morphology. SPARC expression in mammals is developmentally regulated and is highest at sites of extracellular matrix assembly and remodeling such as parietal endoderm and bone. We have isolated cDNA and genomic DNA clones encoding the Caenorhabditis elegans homologue of SPARC. The gene organization is highly conserved, and the proteins encoded by mouse, human, and nematode genes are about 38% identical. SPARC consists of four domains (I-IV) based on predicted secondary structure. Using bacterial fusion proteins containing nematode domain I or the domain IV EF-hand motif, we show that, like the mammalian proteins, both domains bind calcium. In transgenic nematodes expressing a SPARC-lacZ fusion gene, beta-galactosidase staining accumulated in a striated pattern in the more heavily stained muscle cells along the body. Comparison of the pattern of transgene expression to unc-54-lacZ animals demonstrated that SPARC is expressed by body wall and sex muscle cells. Appropriate levels of SPARC are essential for normal C. elegans development and muscle function. Transgenic nematodes overexpressing the wild-type SPARC gene were abnormal. Embryos were deformed, and adult hermaphrodites had vulval protrusions and an uncoordinated (Unc) phenotype with reduced mobility and paralysis.
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PMID:The Caenorhabditis elegans homologue of the extracellular calcium binding protein SPARC/osteonectin affects nematode body morphology and mobility. 825 96

We tested the long-term effects of sublethal oxidative stresses on replicative senescence. WI-38 human diploid fibroblasts (HDFs) at early cumulative population doublings (CPDs) were exposed to five stresses with 30 microM tert-butylhydroperoxide (t-BHP). After at least 2 d of recovery, the cells developed biomarkers of replicative senescence: loss of replicative potential, increase in senescence-associated beta-galactosidase activity, overexpression of p21(Waf-1/SDI-1/Cip1), and inability to hyperphosphorylate pRb. The level of mRNAs overexpressed in senescent WI-38 or IMR-90 HDFs increased after five stresses with 30 microM t-BHP or a single stress under 450 microM H(2)O(2). These corresponding genes include fibronectin, osteonectin, alpha1(I)-procollagen, apolipoprotein J, SM22, SS9, and GTP-alpha binding protein. The common 4977 bp mitochondrial DNA deletion was detected in WI-38 HDFs at late CPDs and at early CPDs after t-BHP stresses. In conclusion, sublethal oxidative stresses lead HDFs to a state close to replicative senescence.
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PMID:Induction of replicative senescence biomarkers by sublethal oxidative stresses in normal human fibroblast. 1069 47

Stress-induced premature senescence (SIPS) is induced 3 days after exposure of human diploid fibroblasts to subcytotoxic oxidative stress with H(2)O(2), with appearance of several biomarkers of replicative senescence. In this work, we show that transforming growth factor-beta1 (TGF-beta1) regulates the induction of several of these biomarkers in SIPS: cellular morphology, senescence-associated beta-galactosidase activity, increase in the steady-state level of fibronectin, apolipoprotein J, osteonectin, and SM22 mRNA. Indeed, the neutralization of TGF-beta1 or its receptor (TGF-beta RII) using specific antibodies decreases sharply the percentage of cells positive for the senescent-associated beta-galactosidase activity and displaying a senescent morphology. In the presence of each of these antibodies, the steady-state level of fibronectin, osteonectin, apolipoprotein J, and SM22 mRNA is no more increased at 72 h after stress. Results obtained on fibroblasts retrovirally transfected with the human papillomavirus E7 cDNA suggest that retinoblastoma protein (Rb) regulates the expression of TGF-beta1 in stressful conditions, leading to SIPS and overexpression of these four genes.
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PMID:Subcytotoxic H2O2 stress triggers a release of transforming growth factor-beta 1, which induces biomarkers of cellular senescence of human diploid fibroblasts. 1106 Feb 95

Human diploid fibroblasts (HDFs) exposed to subcytotoxic stresses under H2O2, tert-butylhydroperoxide (t-BHP), and ethanol (EtOH) undergo stress-induced premature senescence (SIPS) characterized by many biomarkers of HDFs replicative senescence. Among these biomarkers are a growth arrest, an increase in the senescence-associated beta-galactosidase activity, a senescent morphology, an overexpression of p21waf-1 and the subsequent inability to phosphorylate pRb, the presence of the common 4977-bp mitochondrial deletion, and an increase in the steady-state level of several senescence-associated genes such as apolipoprotein J (apo J). Apo J has been described as a survival gene against cytotoxic stress. In order to study whether apo J would be protective against cytotoxicity SIPS and replicative senescence in human fibroblasts, a full-length complementary deoxyribonucleic acid of apo J was transfected into WI-38 HDFs and SV40-transformed WI-38 HDFs. The overexpression of apo J resulted in an increased cell survival after t-BHP and EtOH stresses at cytotoxic concentrations. In addition, when WI-38 HDFs were exposed to 5 subcytotoxic stresses with EtOH or t-BHP, in conditions that were previously shown to induce SIPS, a lower induction of 2 biomarkers of SIPS was observed in HDFs overexpressing apo J. No effect of apo J overexpression was observed on the proliferative life span of HDFs, even if apo J overexpression triggered osteonectin (SPARC) overexpression, which was shown to decrease the mitogenic potential of platelet-derived growth factor but not of other common growth-inducing conditions. Apo J senescence-related overexpression is proposed to have antiapoptotic rather than antiproliferative effects.
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PMID:Overexpression of apolipoprotein J in human fibroblasts protects against cytotoxicity and premature senescence induced by ethanol and tert-butylhydroperoxide. 1189 85

In this work, we show that repeated stresses with UVB (290-320 nm) induce stress-induced premature senescence (SIPS) of skin human diploid fibroblasts (HDFs). HDFs at early cumulative population doublings were exposed three or five times to increasing subcytotoxic doses of UVB with one stress per day. After 2 days of recovery, several biomarkers of replicative senescence were established. First, there was an increase in the proportion of cells positive for senescence-associated beta-galactosidase activity. Second, there was a loss of replicative potential as assessed by a very low level of [3H]-thymidine incorporation. Third, the steady-state level of the mRNA of three senescence-associated genes, i.e. fibronectin, osteonectin and SM22, was increased in HDFs at 72 h after three and five exposures to UVB. In conclusion, these results suggest that it is possible to induce SIPS in HDFs after repeated exposures to subcytotoxic doses of UVB. This model could be used to test whether HDFs in UVB-induced premature senescence are able to promote epithelial cell growth and tumorigenesis in skin, as shown recently with HDFs in H(2)O(2)-induced premature senescence.
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PMID:UVB-induced premature senescence of human diploid skin fibroblasts. 1220 29

Chronic exposure to solar UV irradiation leads to photoaging, immunosuppression, and ultimately carcinogenesis. Cellular senescence is thought to play an important role in tumor suppression and apoptosis resistance. However, the relationships among stress-induced premature senescence (SIPS), tumorigenesis and apoptosis induced by UVB remain unknown. We developed a model of UVB-induced premature senescence in human skin fibroblasts (HSFs). After five repeated subcytotoxic UVB exposures at a dose of 10 mJ/cm2, the following biomarkers of senescence were markedly present: senescence-associated beta-galactosidase (SA beta-gal) activity, growth arrest, and the overexpression of senescence-associated genes. Firstly, there was an increase in the proportion of cells positive for SA beta-gal activity. Secondly, there was a loss of replicative potential as assessed by MTT assay. FACS analysis showed that UVB-stressed HSFs were blocked mostly in the G1 phase of the cell cycle, and replicative senescence, and protein expression of p53, p21(WAF-1) and p16(INK-4a) increased significantly. Thirdly, the mRNA levels of three senescence-associated genes, fibronectin, osteonectin and SM22, also increased. A real time PCR array to investigate the mRNA expression of p53-related genes involved in growth arrest, apoptosis and tumorigenesis indicated that p53, p21, p19, Hdm2, and Bax were up-regulated, and bcl, HIF-1alpha and VEGF were down-regulated. Collectively, our data suggest that UVB-induced SIPS plays an important role in p53-related apoptosis resistance and tumor suppression activity.
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PMID:p53-related apoptosis resistance and tumor suppression activity in UVB-induced premature senescent human skin fibroblasts. 1842 58