Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been shown previously that maternal mRNA, synthesized and stored in growing oocytes, is stabilized and blocked from translation through various mechanisms including restricted polyadenylation and the binding of proteins to 3' regulatory elements. In addition to binding sequence-specific proteins, the bulk of stored mRNA is packaged with a set of 'masking' proteins, the most abundant of which are the phosphoproteins pp56 and pp60. In this report these proteins are shown to be bound to heterogeneous mRNA sequences and not to the 3' poly(A) tract. Crosslinking studies demonstrate that all of the pp56/60 present makes direct contact with the RNA. In vitro binding studies confirm that pp56/60 interact with single-stranded RNA of heterogeneous sequence, such as occurring in the maternal mRNA encoding cyclin B1. However, binding is equally effective to capped and polyadenylated cyclin mRNA, to truncated mRNA lacking 5' and 3' non-coding regions and even to the antisense sequence. Lengths of 70-80 nucleotides are protected from ribonuclease digestion after protein binding. Although no extended binding motif could be detected, binding does appear to have some specificity in that it is not competed out by 100-fold excess of double-stranded RNA, transfer RNA, poly(A) and various other homopolymers and heteropolymers. The sequence which competes most efficiently is the mixed polypyrimidine, poly(C,U). Crosslinking of RNA-protein complexes, followed by ribonuclease digestion, suggests that the arrangement of proteins on RNA is as dimers. Dimerization appears to be stabilized by phosphorylation of pp56/60. These results are discussed in terms of the known structures of pp56/60.
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PMID:Binding of Xenopus oocyte masking proteins to mRNA sequences. 145 24

Stable, nonradioactive riboprobes were used in ribonuclease protection assays to monitor the changes in cyclin mRNA expression during cell cycle progression in human mammary epithelial cells. Probes labeled with biotin demonstrated sufficient sensitivity (comparable to 32P) to detect these low-abundance mRNAs and thus offer a safe and easy alternative to traditional radioactive assays. Three detection systems based on chemiluminescence generated by horseradish peroxidase or alkaline phosphatase were compared for sensitivity, background and ease of use.
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PMID:Detection of cyclin messenger RNAs by nonradioactive ribonuclease protection assay: a comparison of four detection methods. 858 15

Ovarian-derived estradiol plays a critical endocrine role in the regulation of gonadotropin synthesis and secretion from the hypothalamic-pituitary axis. In turn, several para/autocrine effects of estrogen within the ovary are known, including increased ovarian weight, stimulation of granulosa cell growth, augmentation of FSH action, and attenuation of apoptosis. The estrogen receptor-alpha (ERalpha) is present in all three components of the hypothalamic-pituitary-ovarian axis of the mouse. In contrast, estrogen receptor-beta (ERbeta) is easily detectable in ovarian granulosa cells but is low to absent in the pituitary of the adult mouse. This distinct expression pattern for the two ERs suggests the presence of separate roles for each in the regulation of ovarian function. Herein, we definitively show that a lack of ERalpha in the hypothalamic-pituitary axis of the ERalpha-knockout (alphaERKO) mouse results in chronic elevation of serum LH and is the primary cause of the ovarian phenotype of polycystic follicles and anovulation. Prolonged treatment with a GnRH antagonist reduced serum LH levels and prevented the alphaERKO cystic ovarian phenotype. To investigate a direct role for ERalpha within the ovary, immature alphaERKO females were stimulated to ovulate with exogenous gonadotropins. Ovulatory capacity in the immature alphaERKO female was reduced compared with age-matched wild-type (14.5+/-2.9 vs. 40.6+/-2.6 oocytes/animal, respectively); however, oocytes collected from the alphaERKO were able to undergo successful in vitro fertilization. A similar discrepancy in oocyte yield was observed after superovulation of peripubertal (42 days) wild-type and alphaERKO females. In addition, ovaries from immature superovulated alphaERKO females possessed several ovulatory but unruptured follicles. Investigations of the possible reasons for the reduced number of ovulations in the alphaERKO included ribonuclease protection assays to assess the mRNA levels of several markers of follicular maturation and ovulation, including ERbeta, LH-receptor, cyclin-D2, P450-side chain cleavage enzyme, prostaglandin synthase-2, and progesterone receptor. No marked differences in the expression pattern for these mRNAs during the superovulation regimen were observed in the immature alphaERKO ovary compared with that of the wild-type. Serum progesterone levels just before ovulation were slightly lower in the alphaERKO compared with wild-type. These studies indicate that treatment of alphaERKO females with a GnRH antagonist decreased the serum LH levels to within the wild-type range and concurrently prevented development of the characteristic ovarian phenotype of cystic and hemorrhagic follicles. Furthermore, a lack of functional ERalpha within the ovary had no effect on the regulation of several genes required for follicular maturation and ovulation. However, the reduced numbers of ovulations following the administration of exogenous gonadotropins in the alphaERKO suggests an intraovarian role for ERalpha in follicular development and ovulation.
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PMID:Prevention of the polycystic ovarian phenotype and characterization of ovulatory capacity in the estrogen receptor-alpha knockout mouse. 1057 51

We have shown earlier that the cell growth inhibitory activity of interferon (IFN) is significantly enhanced by tunicamycin (TM) (Maheshwari et al., Science 219, 1339-1341, 1983). In this report, we investigated various regulatory points of synergistic action between TM and IFN-alpha/beta that inhibit cell growth in NIH 3T3 cells. The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) viability assays showed a dose-dependent increase in percentage inhibition of the cells when treated with either TM or IFN. When doses of TM and IFN that had no significant inhibition on cell viability were used in combination, there was a pronounced suppression of DNA synthesis (tritiated thymidine incorporation). Flow cytometry studies revealed that individual treatments with either IFN or TM that did not alter the cell cycle profile, when combined, resulted in an impaired cell cycle by inhibiting G1/S progression. The blockage of G1/S transition was associated with reduction of cyclin-dependent kinase (CDK4) activity. The mRNA (analyzed by ribonuclease protection assay) and protein levels (assayed by Western blotting) of cyclins D1, D3, and CDK4 were downregulated by combined treatment with IFN and TM. An increase in the expression of p27/kipl, an inhibitor of CDK4, was observed in cells that were treated with both IFN and TM. These studies suggest that insufficient formation of the active cyclin/CDK complex could possibly be deferring the cells from normal cycling and may be responsible for the ability of TM to enhance cell growth inhibition induced by IFN.
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PMID:Tunicamycin enhances the anticellular activity of interferon by inhibiting G1/S phase progression in 3T3 cells. 1076 75

The expression of different cell cycle proteins in terminally differentiated neurons apparently precedes cell death or contributes to pathogenetic progression of Alzheimer's disease (AD). Cyclins and cyclin-dependent kinases (Cdks), physiologically involved in mitotic processes of proliferating cells, are elevated in neurons prone to dedifferentiation and degeneration. Previously, it was shown that even inhibitors of the Cdks as p16(INK4a), p18(INK4c) or p27(KIP1) are expressed in neurons of AD patients, indicating a rather complete involvement of cell cycle machinery in affected neurons. The aim of this study was to examine the involvement of the non-classical cyclin C in the pathogenetic process of AD. A marked elevated immunoreactivity of cyclin C was found both in neurons and astrocytes in AD. Increased levels of cyclin C RNA were detected by ribonuclease protection assay (RPA) in severe AD cases. Colocalization of cyclin C and its preferred binding partner, Cdk8, was only observed in astrocytes but not in neurons. The present observations suggest different cellular functions of cyclin C in neurons and astrocytes in AD.
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PMID:Cyclin C expression is involved in the pathogenesis of Alzheimer's disease. 1260 Jul 19