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)

Treatment of murine leukemia virus reverse transcriptase (MuLV RT) with 4-(oxoacetyl)-phenoxyacetic acid (OAPA) results in the loss of DNA polymerase as well as template-primer binding activity but has no effect on the RT-associated RNase-H activity. Binding stoichiometry revealed that approximately 3 mol of OAPA bound per mole of enzyme, when complete enzyme activation occurred. However, in the presence of template-primer, OAPA does not abolish polymerase activity and 2 mol of OAPA remains bound to 1 mol of enzyme. This observation suggests that only one OAPA reactive site is responsible for the loss of polymerase activity. This site was located on a single tryptic peptide by comparing the maps of the native enzyme and the enzyme treated with OAPA in the presence and absence of template-primer. The appearance of a new peptide peak eluting at 125 min from a C-18 reverse-phase column was consistently noted in the tryptic digest of enzyme treated with OAPA. This peak was absent in tryptic peptides made from the control enzyme or the enzyme protein that was treated with OAPA in the presence of activated DNA or synthetic template-primers. Amino acid composition and sequence analyses of this peptide revealed that it spanned residues 312-342 in the primary amino acid sequence of MuLV RT. Since this peptide does not contain arginine residues and Lys-329 exhibited resistance to tryptic digestion, we conclude that Lys-329 is the target of OAPA action.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lysine-329 of murine leukemia virus reverse transcriptase: possible involvement in the template-primer binding function. 169 96

It has long been known that lesions of the hypothalamus lead to female sexual precocity. While an increased production of luteinizing hormone-releasing hormone (LHRH), the neurohormone that controls sexual development, appears to mediate the advancement of puberty induced by these lesions, little is known about the mechanism(s) by which hypothalamic injury activates LHRH secretion. Since brain lesions result in accumulation of neurotrophic/mitogenic activities in the injured area, we tested the hypothesis that transforming growth factor alpha (TGF-alpha), a mitogenic polypeptide recently shown to stimulate LHRH release, is produced in response to hypothalamic injury and mediates the effect of the lesion on puberty. Radiofrequency lesions of the preoptic area-anterior hypothalamic area (POA-AHA) of 22-day-old female rats resulted in precocious puberty within 7 days after the operation. RNA blot hybridization revealed that lesion-induced puberty was preceded by an increase in TGF-alpha mRNA levels in the POA-AHA. Epidermal growth factor (EGF) mRNA was undetectable in both intact and lesioned hypothalami. TGF-alpha mRNA levels, quantitated by RNase protection assays, were 3.5-fold greater in lesioned animals approaching puberty than in age-matched controls. Immunohistochemical studies, utilizing single- and double-staining procedures, demonstrated the presence of TGF-alpha precursor-like immunoreactivity in reactive astrocytes surrounding the lesion site. Hybridization histochemistry showed increased TGF-alpha mRNA expression in cells of the same area, further implicating reactive astrocytes as a site of TGF-alpha synthesis. The actions of TGF-alpha are mediated by its interaction with EGF receptors. Continuous infusion of RG-50864, an inhibitor of EGF receptor kinase activity, at the site of injury prevented the advancement of puberty induced by the lesion. These results suggest that TGF-alpha acting via EGF-like receptors contributes to the acceleration of puberty induced by anterior hypothalamic lesions. They also indicate that activation of TGF-alpha gene expression in glial cells is a component of the hypothalamic response to injury.
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PMID:Transforming growth factor alpha contributes to the mechanism by which hypothalamic injury induces precocious puberty. 194 96

The rat preoptic area-anterior hypothalamic continuum (POA-AH) contains about 400-800 neurons that express the decapeptide GnRH and the 56-amino-acid GnRH-associated peptide. Originating from the olfactory placode, these neurons migrate and establish their final distribution and connections in the POA-AH several days before birth. The aim of the present study was to examine whether the biosynthesis of the mRNA encoding the precursor (proGnRH) common to GnRH and GnRH-associated peptide undergoes postnatal changes corresponding to the development of sexual maturation. The POA-AH content of proGnRH messenger RNA (mRNA) was followed from postnatal day 1 to day 90 in female and male Sprague-Dawley rats killed by decapitation between 1000-1200 h. Cytoplasmic RNA fractionated from individual POA-AH homogenates was purified using proteinase K digestion. Cytoplasmic proGnRH mRNA was quantitated simultaneously with cyclophilin mRNA (an internal standard control) using solution hybridization-RNase protection assay, with the protected fragments separated through polyacrylamide gel electrophoresis. In the POA-AH, the concentrations of proGnRH mRNA (femtograms mRNA per microgram total RNA) increased significantly with age in both sexes (P less than 0.001). In males, proGnRH mRNA levels increased by day 30 some 2-fold over the values of days 5 and 10, and the levels established on day 30 were maintained through adulthood. In females, the first rise in proGnRH mRNA levels occurred on day 30, followed by an additional increase on day 45 to levels seen in adulthood. Levels of proGnRH mRNA established in adulthood were significantly higher in females than in males (P less than 0.03). The concentrations of cyclophilin mRNA (picograms mRNA per microgram total RNA) remained essentially unchanged in both sexes during the same period of time when proGnRH mRNA levels were increasing. These results provide evidence for postnatal sex-related increases in the levels of proGnRH mRNA in the rat POA-AH, which are likely to reflect differential regulation by gonadal steroids.
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PMID:Postnatal development of gonadotropin-releasing hormone and cyclophilin gene expression in the female and male rat brain. 203 56

In the last decades several markers of pancreatic neoplasia have been proposed to obtain a diagnosis as earlier as possible. Prerequisites of a good tumor marker are high sensitivity and specificity. Among the various substances, serum determination of pancreatic enzymes has been found of no utility in early diagnosis of pancreatic cancer, due to its lack in sensitivity and specificity. Similar results with ribonuclease and deoxyribonuclease. Oncofetal antigens (CEA and POA) have been initially considered promising indices; however, further studies showed their limits. In particular CEA is greatly influenced by the presence of hepatic metastases; therefore, serum levels are detectable only in advanced stages. TPA is characterized by a high sensitivity, but lacks in specificity and its use is now avoided. A real progress in the field of tumor markers has been made in the last years with the monoclonal antibody technique: among them CA 19-9 showed a good sensitivity and a satisfactory specificity as regards the diagnosis of pancreatic cancer. However, it cannot be considered as absolute aid, since it is influenced by several factors, as tumor spread, jaundice and liver dysfunction.
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PMID:[Value and limitations of neoplasm markers in the diagnosis of pancreatic carcinoma]. 204 59

Cancer grows in interaction with the host, that is, a host-tumor relationship exists. Investigations of host factors in patients receiving cancer chemotherapy are important, as they reveal the conditions in which a tumor response can develop. Furthermore, reliable host factors, if present, will be useful for quantitative evaluation of the effects of treatment. We have investigated the following three categories of host factors in relation to the effects of cancer chemotherapy and/or immunotherapy. CBC, and blood chemistries (44 parameters). Tumor markers; sialic acid, RNase, lysozyme, ferritin, IAP (immunosuppressive acidic protein), elastase I, AFP, CEA, POA, CA 19-9, CA 125, etc. Immunological parameters; lymphocyte, active T cell, T cell, B cell, IgG Fc receptor-positive T cell, lymphocyte blastogenesis stimulated by PHA, or concanavalin-A, ADCC activity, interferon production in vitro induced by poly I: C, or PHA, PPD skin test, immune complex, immunoglobulin G, A, and M, OKT series 3, 4, 8, 11, 4/8 ratio, antihuman HLA-DR, Leu 11, NK cell activity, etc. From our clinical observations, there were no significant differences in the pretreatment levels of these parameters between responders and non-responders. In responders, there was a tendency for the host factors to show greater degrees of improvement following treatment than in non-responders, but none proved to be reasonably reliable parameters for evaluating therapeutic effects. On the other hand, from our clinical observations on the advanced gastric cancer cases, life span showed a close correlation with tumor regression induced by cancer chemotherapy. Because of these facts, it is only natural that the clinical effects of chemotherapy are currently determined by definite tumor regression.
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PMID:[Host factors in cancer chemotherapy]. 372 33

Oncofetal markers for colon carcinomas are CSAp, a nonsulfated mucin, a second trimester fetal antigen, an altered thymidine kinase, a monosialoganglioside, and glycolipid antigens. For gastric carcinoma, they are basic fetoprotein, a sulfoglycoprotein, and for pancreatic carcinomas--POA, an oncofetal pancreatic antigen, and designated as CAPI, an oncofetal antigen. Tumor-associated markers for colon carcinomas are: UDP-galactosyltransferase and zinc glycinate marker; for gastric carcinomas, sulfated glycoprotein and for pancreatic carcinomas, pancreas carcinoma-associated antigen, a polycytidylic acid-specific ribonuclease, and galactosyltransferase. Suggested as tumor-specific markers for colon carcinomas are an altered mucoprotein, basic antigen, beta 2-microglobulin-associated antigen, and a specific adenosine deaminase; for gastric carcinomas, a specific protein, an antigen with 3-oxyanthranilic acid, and an antigen of unknown origin in gastric secretions; for pancreatic carcinomas, an antigen with molecular weight of 380,000 daltons and an antigen suggested by tumor immunity.
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PMID:Gastrointestinal tumor markers, other than carcinoembryonic antigen, and alpha fetal protein. 688 74

The precursor of gonadotropin-releasing hormone (GnRH) and the 56-amino acid GnRH-associated peptide is encoded in an mRNA of about 560 bases in length. This mRNA derives from an approximately 4300-base pair-long gene consisting of four relatively short exons (denoted 1, 2, 3, and 4) and three large introns (A, B, and C). In this study, we characterized the order by which the three introns are spliced from the primary transcript and processing intermediates to give rise to a mature mRNA and evaluated the potential role of gene transcription and pre-mRNA processing in the control of proGnRH mRNA levels in vivo. Nuclear and cytoplasmic RNA fractions isolated from rat preoptic area-anterior hypothalamus (POA-AH) and basal olfactory area (located rostral to the POA) were analyzed by 1) solution hybridization-RNase protection mapping using several RNA probes directed at various regions of the proGnRH gene and 2) reverse transcription-polymerase chain reaction using several oligonucleotide primers. Both types of analysis showed that proGnRH pre-mRNA processing begins with the splicing of intron B from the primary gene transcript. Hence, intron B is the ideal target for studying proGnRH primary transcript by in situ hybridization. Subsequent splicing of introns A and C appeared to take place in two alternative, although not equally prevalent pathways. Quantitative analysis indicated that the proGnRH hnRNA species constituted, on a mole basis, about 20% of the total gene transcripts in the POA-AH. The primary transcript alone constituted about 10% of the total gene transcripts in the POA-AH and as much as 20% in the basal olfactory area. The prospect of blockade of proGnRH hnRNA processing by means of hybridization with endogenous antisense RNAs (transcribed from the SH gene on the opposite strand of the same DNA locus) did not prove to be likely, as the SH transcripts were present at very low levels compared to any of the proGnRH RNA species. We conclude that the relatively large pool of proGnRH hnRNA may reflect a high rate of gene transcription and/or slow RNA processing.
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PMID:Processing of gonadotropin-releasing hormone gene transcripts in the rat brain. 830 66

Injury of the nervous system triggers a complex series of repair mechanisms that include production of neurotrophic and mitogenic factors by cells neighboring the injured area. While trauma of most parts of the brain results in loss of function, lesions of certain regions of the female hypothalamus enhance the secretory activity of a group of specialized neurons that produce luteinizing hormone-releasing hormone (LHRH), the neuropeptide that controls sexual development. The increased output of LHRH causes sexual precocity by prematurely activating the neuroendocrine reproductive axis. Recent studies have implicated transforming growth factor alpha (TGF alpha) produced by reactive astrocytes in the process by which lesions hasten sexual maturation, and have suggested that the stimulatory actions of TGF alpha on LHRH neurons require the intermediacy of epidermal growth factor receptors (EGFRs). In the present study, we examined the changes in EGFR gene expression following lesions of the preoptic-anterior hypothalamic area (POA-AHA) of immature female rats, identified the cell types where EGFR synthesis increases, and assessed the biochemical activity of the newly formed EGFR protein. RNase protection assays demonstrated that the lesion significantly increased the levels of a predominant mRNA transcript encoding the full-length, membrane-spanning EGFR, but did not affect those of a much less abundant, alternatively spliced mRNA that encodes a truncated, presumably secreted form of EGFR. Following lesions, antibody-induced EGFR kinase activity increased twofold. Antibodies directed against a peptide sequence contained within the carboxy terminus of EGFR showed intense EGFR immunoreactivity in cells surrounding the lesion site; double immunohistochemistry identified these cells as astrocytes since EGFR immunoreactivity was colocalized with that of glial fibrillary acidic protein, an astrocytic marker. That these changes result from an increase in EGFR gene expression was indicated by the elevated levels of EGFR mRNA detected by in situ hybridization in cells of the same area. Although POA-AHA lesions did not result in appearance of EGFR in LHRH neurons themselves, EGFR-positive cells and processes were seen in close proximity to LHRH neurons and their nerve terminals, particularly in the area surrounding the lesion. Since TGF alpha gene expression is also increased in reactive astrocytes of POA-AHA lesions and blockade of EGFR prevented the advancing effect of the lesion on puberty (Junier et al., 1991b), the present results support the concept that, in lesioned animals, TGF alpha stimulates LHRH secretion indirectly via a paracrine mechanism that involves its interaction with EGFRs located on astroglial cells.
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PMID:Hypothalamic lesions that induce female precocious puberty activate glial expression of the epidermal growth factor receptor gene: differential regulation of alternatively spliced transcripts. 842 32

We have characterized the nuclear and cytoplasmic RNA transcripts derived from the gonadotropin releasing hormone (GnRH) gene in a mouse hypothalamic neuronal GT1 cell line. Analyses of nuclear GnRH RNA precursors present in the GT1 cells by RNase protection assay show that there is no particular order of intron excision, suggesting the existence of multiple processing pathways. A similar pattern is observed in mouse preoptic area-anterior hypothalamus (POA-AH). In GT1 cells, approximately 5% of the total GnRH RNA transcripts are found in the nucleus. In contrast, in the POA-AH of mice, nuclear transcripts comprise 40% of the total GnRH transcripts. Thus the GT1 cells, while similar in overall GnRH RNA processing to mouse hypothalamic GnRH neurons, do not exhibit the high abundance of nuclear GnRH RNA transcripts seen in the rodent GnRH neuron in vivo. Quantitative analysis of the nuclear RNA species shows that the GnRH primary transcript comprises more than 90% of the total nuclear GnRH mRNA precursors in both GT1 cells and mouse POA-AH and thus GnRH processing intermediates account for fewer than 10% of these precursors. Using these probes, we have examined changes in GnRH primary transcript expression in GT1-7 cells. In the presence of RNA synthesis inhibitors, the half-life of the GnRH primary transcript was found to be quite short, approximately 18 min, suggesting that the level of primary transcript would reflect levels of GnRH gene transcription. When GT1-7 cells are treated with the phorbol ester PMA (phorbol, 12-myristate, 13-acetate) for 1 h, GnRH primary transcript levels decrease by approximately 70%. Supporting the hypothesis that GnRH primary transcript is a good indicator of GnRH gene transcription is the finding that 1 h of PMA treatment results in a similar (approximately 50%) decrease in GnRH gene transcription, as assayed by nuclear run-on assay. Our observation that GT1 cells resemble mouse hypothalamic GnRH neurons in their pattern of intron excision and in the ratio of primary transcript to other nuclear transcripts emphasizes the utility of these cells for studying the regulation of GnRH gene expression in this immortalized hypothalamic cell line.
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PMID:Characterization of gonadotropin-releasing hormone gene transcripts in a mouse hypothalamic neuronal GT1 cell line. 901 81

The preoptic regulatory factor genes, PORF-1 and PORF-2, are expressed in the rat brain in a regional-, age- and gender-dependent fashion. They are also expressed in the testis, where PORF-2 mRNA localizes to dividing germ cells while PORF-1 mRNA is associated with newly differentiated sperm. This suggests that PORF-1 and PORF-2 may play distinct roles in cell growth and differentiation. Moreover, the two preoptic regulatory factors are also highly expressed in the immature and mature rat hypothalamus, and their expression is modulated by gonadal hormones. Therefore, in the present study we investigated the expression of these two factors in neuroendocrine regions of the developing rat brain by addressing the following questions. First, are PORF-1 and PORF-2 mRNAs expressed during perinatal development in the preoptic area-anterior hypothalamus (POA-AH) and medial basal hypothalamus (MBH), and how do their levels vary? Second, are there gender differences in their expression? We also compared expression of the PORF mRNAs with those of neuropeptide Y (NPY) and gonadotropin-releasing hormone (GnRH), which play critical neuroendocrine roles, in these brain regions. PORF-1, PORF-2, and NPY mRNAs in the POA-AH and MBH, and GnRH mRNA in the POA-AH, were quantified by RNase protection assay at embryonic day (E) 18-19, and postnatal days (P) 0, 5, 10 and 15 in male and female rats. The results show that the four neuropeptide genes are regulated differentially during the perinatal-prepubertal period. PORF-1 mRNA shows age-related increases in expression from E18-E19 to P15 in POA-AH and MBH, without significant gender differences. In contrast, PORF-2 mRNA shows both age and gender differences in expression in these brain regions, with decreases occurring during the same time period in development. NPY mRNA increases similarly in males and females with age in POA-AH and MBH during this period. GnRH mRNA does not change during this period. Taken together with previous studies, the results suggest possible roles for PORF-1 and NPY in the pubertal process, since their expression is maximal from the prepubertal to the early pubertal period. The observation of highest levels of expression of PORF-2 in embryonic neuroendocrine tissues suggests a possible involvement of this neuropeptide in prenatal/neonatal developmental events.
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PMID:Perinatal developmental changes in expression of the neuropeptide genes preoptic regulatory factor-1 and factor-2, neuropeptide Y and GnRH in rat hypothalamus. 1058 30


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