Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Na(+)-independent neutral amino acid transporter (NAA-Tr) that we had previously cloned from rat kidney has been investigated with respect to its distribution in mammalian tissues and cells. By Northern blot analysis and RNase protection assay, a 2.4-kilobase (kb) mRNA in rat intestine was found to be identical to that in rat kidney. Of the other rat tissues examined, only brain and heart were found to contain mRNAs related to kidney NAA-Tr by Northern assay. However, these were larger (approximately 5 and approximately 7 kb). Mouse and rabbit kidney also contain mRNAs of 2.4 kb that exhibited a high degree of homology with rat kidney NAA-Tr. Of the several cultured cells investigated that demonstrated considerable Na(+)-independent neutral amino acid transport activity, only human colon carcinoma (Caco) cells were positive by Northern assay. The failure to detect NAA-Tr mRNA in many cells and tissues that carry out Na(+)-independent transport indicates that unrelated transporters must also exist. Cells and tissues that were negative with respect to rat kidney NAA-Tr as well as those that were positive transported leucine and tryptophan equally well. However, when mRNA from the same cells and tissues was expressed in oocytes, in all cases tryptophan was transported far less efficiently than leucine. This defect in tryptophan transport is apparently due to aberrant expression of neutral amino acid transporters in general in Xenopus oocytes.
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PMID:Distribution of mRNA of a Na(+)-independent neutral amino acid transporter cloned from rat kidney and its expression in mammalian tissues and Xenopus laevis oocytes. 143 48

We evaluated the interaction of a biochemically active concentration of cyclopentenyl cytosine (CPE-C), an investigational antimetabolite which inhibits CTP synthetase, on the cytotoxicity of arabinosyl-5-azacytosine (Ara-AC) and 1-beta-D-arabinofuranosylcytosine (Ara-C) in HCT 116 colon carcinoma cells. A 3-h exposure to 0.5 microM CPE-C depleted CTP pools by over 90% and decreased dCTP pools by 57%; the effect on CTP pools persisted for up to 24 h following washout of CPE-C. A 3-h pre-exposure to 0.5 microM CPE-C augmented the growth inhibition resulting from a 24-h exposure to Ara-AC. The combination of 1 microM cytidine and deoxycytidine fully reversed the enhancement associated with CPE-C pretreatment, to a level of growth inhibition expected from either CPE-C or Ara-AC alone. A striking enhancement of toxicity was observed in clonogenic studies with pre-exposure to CPE-C at a nonlethal dose followed by either Ara-AC or Ara-C. CPE-C increased the formation of Ara-AC and Ara-C nucleotides by as much as 3-fold, and this was accompanied by increased incorporation of the arabinosyl nucleotides into methanol-precipitable material. Analysis of purified RNase-treated nucleic acids by cesium sulfate density centrifugation confirmed that a 3-h pre-exposure to CPE-C increased [3H]-Ara-C incorporation into DNA at 4 and 24 h by 2.4- and 2.7-fold, respectively. Thus, these studies indicate that CPE-C can function as a biochemical modulator. Following a brief exposure to a nonlethal concentration, CPE-C is capable of augmenting the cytotoxicity and intracellular metabolism of Ara-AC and Ara-C.
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PMID:Enhancement of the toxicity and DNA incorporation of arabinosyl-5-azacytosine and 1-beta-D-arabinofuranosylcytosine by cyclopentenyl cytosine. 169 59

Transforming growth factor-beta 1 (TGF-beta 1) has previously been implicated as a potential negative autocrine or paracrine growth regulator of certain cell types (Arteaga, C. L., R. J. Coffey, Jr., T. C. Dugger, C. M. McCutchen, H. L. Moses, and R. M. Lyons. 1990. Cell Growth & Differ. 1:367-374; Hafez, M. M., D. Infante, S. Winawer, and E. Friedman. 1990. Cell Growth & Differ. 1:617-626; Glick, A. B., K. C. Flanders, D. Danielpour, S. H. Yuspa, and M. B. Sporn. 1989. Cell Regulation. 1:87-97). This is based mainly on experiments assessing the effects of exogenous TGF-beta 1 or neutralizing antibodies to TGF-beta 1 on normal or tumor cell proliferation in vitro. However, direct evidence demonstrating such a negative regulation of tumor cell growth in vivo is still lacking. To overcome this problem we have constructed and used an antisense expression vector for TGF-beta 1 as a means of regulating endogenous TGF-beta 1 expression in tumor cells. Antisense-transfected FET human colon carcinoma cells showed a fivefold reduction in TGF-beta 1 mRNA and 15-fold reduction in TGF-beta 1 secretion. Antisense mRNA was detected in transfected cells by an RNase protection assay. Compared to control cells, cultured antisense-transfected cells showed a reduction in lag phase time rather than a change in doubling time. Cloning efficiencies of transfected cells were four times greater than control cells in anchorage-independent assays. Control cells did not form tumors at 5 x 10(5) in athymic nude mice. Antisense-transfected cells formed tumors in 40% of animals injected. At higher inocula (1 x 10(6) cells) antisense-transfected cells formed tumors in 100% of animals injected, but control cells still failed to form tumors. These results show that TGF-beta 1 acts as a negative growth regulator of human colon carcinoma cells in vivo as well as in vitro. Acquisition of partial or full resistance to such inhibitory effects may therefore contribute to tumor development and progression.
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PMID:TGF-beta 1 is an autocrine-negative growth regulator of human colon carcinoma FET cells in vivo as revealed by transfection of an antisense expression vector. 173 Jul 43

Chromosomes were isolated from a variety of human cell types using a HEPES-buffered hypotonic solution (pH 8.0) containing KCl, MgSO4, dithioerythritol, and RNase. The chromosomes isolated by this procedure could be stained with a variety of fluorescent stains including propidium iodide, chromomycin A3, and Hoechst 33258. Addition of sodium citrate to the stained chromosomes was found to improve the total fluorescence resolution. High-quality bivariate Hoechst vs. chromomycin fluorescence distributions were obtained for chromosomes isolated from a human fibroblast cell strain, a human colon carcinoma cell line, and human peripheral blood lymphocyte cultures. Good flow karyotypes were also obtained from primary amniotic cell cultures. The Hoechst vs. chromomycin flow karyotypes of a given cell line, made at different times and at dye concentrations varying over fourfold ranges, show little variation in the relative peak positions of the chromosomes. The size of the DNA in chromosomes isolated using this procedure ranges from 20 to over 50 kilobases. The described isolation procedure is simple, it yields high-quality flow karyotypes, and it can be used to prepare chromosomes from clinical samples.
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PMID:Preparation and bivariate analysis of suspensions of human chromosomes. 257 81

In most tissues, ribonucleases (RNases) are found in a latent form complexed with ribonuclease inhibitor (RI). To examine whether these so-called cytoplasmic RNases belong to the same superfamily as pancreatic RNases, we have purified from porcine liver two such RNases (PL1 and PL3) and examined their primary structures. It was found that RNase PL1 belonged to the same family as human RNase Us [Beintema et al. (1988) Biochemistry 27, 4530-4538] and bovine RNase K2 [Irie et al. (1988) J. Biochem. (Tokyo) 104, 289-296]. RNase PL3 was found to be a hitherto structurally uncharacterized type of RNase. Its polypeptide chain of 119 amino acid residues was N-terminally blocked with pyroglutamic acid, and its sequence differed at 63 positions with that of the pancreatic enzyme. All residues important for catalysis and substrate binding have been conserved. Comparison of the primary structure of RNase PL3 with that of its bovine counterpart (RNase BL4; M. Irie, personal communication) revealed an unusual conservation for this class of enzymes; the 2 enzymes were identical at 112 positions. Moreover, comparison of the amino acid compositions of these RNases with that of a human colon carcinoma-derived RNase, RNase HT-29 [Shapiro et al. (1986) Biochemistry 25, 7255-7264], suggested that these three proteins are orthologous gene products. The structural characteristics of RNases PL1 and PL3 were typical of secreted RNases, and this observation questions the proposed cytoplasmic origin of these RI-associated enzymes.
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PMID:Primary structure of a ribonuclease from porcine liver, a new member of the ribonuclease superfamily. 261 Dec 66

The mechanism of action of the adenosine analog, neplanocin A (NPC), was investigated in human colon carcinoma cell line HT-29. Cell viability was reduced to 38 and 17% of control by 24-h exposure to 10(-5) and 10(-4) M NPC, respectively. Cytocidal activity was not affected by inhibition of adenosine deaminase with 2'-deoxycoformycin. Concomitant with decreased cell viability was the reduced incorporation of [14C]dThd and [3H]Leu, and to a lesser extent [3H]Urd, into acid-precipitable material. Labeling of rRNA and tRNA during drug treatment for 24 h with [methyl-3H]Met and [14C]Urd revealed that NPC primarily inhibited RNA methylation, and to a lesser extent, RNA synthesis. RNase T2 digests of total RNA indicated that base and 2'-O-methylation were inhibited to approximately the same degree. Metabolites of NPC were measured by reverse-phase high-performance liquid chromatography and it was found that the major drug metabolite was the drug analog of S-adenosylmethionine with little formation of the respective, S-adenosylhomocysteine metabolite. NPC was utilized to a very small degree for RNA synthesis where only 2 and 30 pmol of NPC/A260 were incorporated into rRNA and tRNA after 24-h exposure to 10(-5) and 10(-4) M NPC, respectively. These results indicate that NPC is metabolized to a metabolite of S-adenosylmethionine which is a poor methyl donor for RNA methyltransferases, and that the accompanying decrease in RNA methylation and protein synthesis appears to be related to its cytocidal activity.
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PMID:Neplanocin A. A cyclopentenyl analog of adenosine with specificity for inhibiting RNA methylation. 633 23

Sera from a patient with systemic lupus erythematosus (SLE), tested by indirect immunofluorescence on frozen tissue sections, gave granular cytoplasmic staining of hepatocytes, gastric chief cells, exocrine cells of the pancreas and submandibular glands, and cerebellar Purkinje cells. In acetone-fixed monolayers of rat embryonic fibroblasts, 3T3 cells, mouse neuroblastoma cells, and cells from a human melanoma and colon carcinoma cell line, the sera stained perinuclear cytoplasmic granules which radiated out towards the cell periphery. More mature and differentiated fibroblasts from rat of human foetal lung showed staining of reticular cytoplasmic structures corresponding to phase-dense rough endoplasmic reticulum (RER). Nucleoli were prominently stained in all cultured cells. Serum absorption with ribosomes inhibited all antibody activity but absorption with RNA or with RNase-treated ribosomes resulted only in partial inhibition. Monolayers of RNase-treated fibroblasts gave weaker staining reactions compared to control untreated cultures. These observations suggest that the autoantibody is directed against ribosomal RNA and ribosomal protein present in cytoplasmic polyribosomes, in RER and in nucleoli.
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PMID:Autoantibody to ribosomes and systemic lupus erythematosus. 700 92

Transforming growth factor beta (TGF-beta) has been extensively studied as an exogenous agent that stimulates the expression of extracellular matrix proteins and their cell-surface integrin receptors in a variety of cell types. However, the recent demonstration of autocrine TGF-beta growth effects in a number of cell types suggests that the steady-state expression of extracellular matrix and integrin proteins and their biological activity may also be under autocrine TGF-beta control. Previously, we reported that repression of autocrine TGF-beta 1 activity by constitutive expression of a full-length TGF-beta 1 antisense cDNA led to abrogation of autocrine negative TGF-beta and, as a result, increased tumorigenicity and anchorage-independent growth of a poorly tumorigenic, well-differentiated colon carcinoma cell line designated FET (Wu, S., Theodorescu, D., Kerbel, R. S., Willson, J. K. V., Mulder, K. M., Humphrey, L. E., and Brattain, M. G. (1992) J. Cell Biol. 116, 187-196). Consequently, we have used this model system to study the effects of repression of autocrine TGF-beta 1 activity on the expression of integrin alpha 5 beta 1 and integrin alpha 5 beta 1-mediated cell adhesion to fibronectin. The expression of the integrin alpha 5 subunit was reduced in TGF-beta 1 antisense transfected FET cells at both mRNA and protein levels as determined by RNase protection assays and immunoprecipitation, respectively. Autocrine TGF-beta 1 had no effect on the transcription of integrin alpha 5 and beta 1 subunits, indicating that autocrine TGF-beta 1 may regulate integrin alpha 5 beta 1 expression at the post-transcriptional level. The diminished expression of integrin alpha 5 beta 1 on the cell surface led to the reduced adhesion of TGF-beta 1 antisense transfected cells to fibronectin. This phenomenon could be reversed by treatment with exogenous TGF-beta 1.
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PMID:Autocrine transforming growth factor beta 1 modulates the expression of integrin alpha 5 beta 1 in human colon carcinoma FET cells. 753

We have recently identified a new exon of the CD44 gene and demonstrated abnormal retention of a noncoding section, intron 9, in mRNA from bladder carcinomas. To analyze this further, the present study examined CD44 gene expression in cell lines from 14 esophageal, 3 colonic, and 4 breast carcinomas and in fresh samples from 20 colorectal carcinomas and corresponding normal colonic mucosa, using reverse transcriptase followed by the polymerase chain reaction (RT-PCR). This confirmed that there was abnormal assembly of several exons of the gene in cell lines and in tumor tissues from these organs. However, the most striking new finding was that intron 9 was present in RNA from 11 esophageal, 3 colon, and 1 breast carcinoma cell line, respectively. This was confirmed by RNase and DNase digestion analysis. Moreover, it was detected both in nuclear and cytoplasmic mRNA fractions, indicating that abnormal splicing of pre-mRNA occurs in cancer cells. The abnormal retention of intron 9 in CD44 gene transcripts was also demonstrated in tumor tissues from 16 (80%) of 20 patients with colon carcinoma, but there was no correlation with Dukes' stage. The biological significance of these observations is not yet understood. However, it is clear that, as with the abnormal expression pattern of CD44 variant exons, intron 9 retention is a good-candidate molecular diagnostic tool for colorectal carcinomas.
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PMID:Abnormal retention of intron 9 in CD44 gene transcripts in human gastrointestinal tumors. 754 38

Our in vivo studies in mice have shown that LDL-receptor gene expression is regulated differently in both liver and intestine by dietary cholesterol and dietary saturated fat. While dietary cholesterol serves to regulate at transcriptional levels, dietary fatty acids do not. To study the mechanism of regulation of LDL-receptor by saturated fat and cholesterol at the cellular level, where any secondary effects of long-term feeding in vivo are minimized we used the cultured hepatoma and colon carcinoma cells, HepG2 and Caco2. LDL-receptor activity was determined by 125I-labeled LDL binding and uptake, LDL-receptor protein by Western blotting, LDL-receptor mRNA by RNase protection assay, and relative rates of LDL-receptor mRNA transcription by nuclear 'run-off' assay. Incubation of cells in lipoprotein-deficient serum (LPDS) for 48 h progressively induced LDL-receptor activity and LDL-receptor protein by 5- to 6-fold in HepG2 cells and 2- to 3-fold in Caco2 cells. Absolute levels of LDL-receptor mRNA and relative rates of LDL-receptor mRNA transcription also increased in parallel to the LDL-receptor activity and protein levels in both cell lines. These data suggest that LPDS induced the LDL-receptor gene by transcriptional mechanism. The suppressive effect of 25-hydroxycholesterol on LDL-receptor regulation was studied by incubating HepG2 and Caco2 cells grown either in 10% FCS or 10% LPDS for 24 h and then for 0-24 h with various doses of 25-hydroxycholesterol. In HepG2 cells, LDL-receptor activity and protein mass progressively decreased to 50% of zero time controls over 24 h. LDL-receptor mRNA levels and relative rates of transcription decreased in parallel. In Caco2 cells, 25-hydrocholesterol lowered LDL-receptor activity, mRNA, and transcription by approximately 35%. To examine the effects of palmitate on LDL-receptor regulation, palmitate was complexed with albumin. Palmitate decreased LDL-receptor activity by 25% in HepG2 cells without altering LDL-receptor mass, mRNA levels, or rates of mRNA transcription. Similarly, in Caco2 cells, palmitate decreased LDL-receptor activity and protein mass 30% of controls, but did not change LDL-receptor mRNA levels and/or rates of transcription. The combination of palmitate (0.8 mM) and 25-hydroxycholesterol (2.5-5 micrograms/ml) suppressed LDL-receptor activity by 65% in HepG2 cells and by 52% in Caco2 cells. However, LDL-receptor mRNA decreased by approximately 50% in HepG2 cells and 30-40% in Caco2 cells.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Regulation of low density lipoprotein receptor gene expression in HepG2 and Caco2 cells by palmitate, oleate, and 25-hydroxycholesterol. 759 67


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