Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cellular protein p57/58, now known to be identical to polypyrimidine tract binding protein (PTB), has earlier been shown to specifically bind to the internal ribosome entry sites (IRES) of encephalomyocarditis virus (EMCV) and some other picornaviral RNAs. To elucidate its relevance to the internal initiation, the effect of cloned purified PTB on EMCV IRES directed translation was studied in cytoplasmic extracts of Krebs-2 ascites carcinoma cells partially depleted of endogenous PTB. Addition of PTB to such extracts resulted in a strong stimulation of translation of a beta-glucuronidase (GUS) reporter cistron fused to the EMCV IRES, but had no effect on translation of capped mRNAs, such as beta-globin, and tobacco mosaic virus (TMV) RNAs. PTB was found to exert its effect at the level of 48S pre-initiation complex formation.
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PMID:Pyrimidine tract binding protein strongly stimulates in vitro encephalomyocarditis virus RNA translation at the level of preinitiation complex formation. 808 84

Little is known about the mechanisms that target transcripts for rapid degradation in plants. In mammalian cells, sequences with a high AU content and multiple AUUUA motifs have been shown to cause mRNA instability when present in the 3' untranslated regions of several transcripts. This precedent, coupled with the poor accumulation of AU-rich foreign transcripts in plants (e.g., BT-toxin mRNAs), prompted us to test whether AU sequences could destabilize transcripts in tobacco. To address this question, we made a set of constructs containing sequences with high AU content inserted into the 3' untranslated regions of reporter genes. The stability of the corresponding transcripts was then assayed in stably transformed cell lines of tobacco. These experiments showed that a 60-base sequence containing 11 copies of the AUUUA motif (AUUUA repeat) markedly destabilized a beta-glucuronidase reporter transcript compared to a no-insert control or a 60-base spacer sequence (GC control). Another sequence with an identical A+U content had little effect. The same results were obtained when each sequence was assayed within the 3' untranslated region of a beta-globin reporter transcript. In regenerated transgenic plants, the AUUUA repeat decreased the accumulation of the beta-globin transcript by approximately 14-fold, compared to the GC control. Taken together, our results indicate that the AUUUA repeat is recognized as an instability determinant in plant cells and that the effect is due to the sequence of the element, not simply to the high AU content.
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PMID:The effect of sequences with high AU content on mRNA stability in tobacco. 826 31

DST elements are highly conserved sequences located in the 3' untranslated regions (UTRs) of a set of unstable soybean transcripts known as the small auxin-up RNAs (SAURs). To test whether DST sequences could function as mRNA instability determinants in plants, a model system was developed to facilitate the direct measurement of mRNA decay rates in stably transformed cells of tobacco. Initial experiments established that the chloramphenicol acetyltransferase (CAT) and beta-glucuronidase (GUS) transcripts degraded with similar half-lives in this system. In addition, their decay kinetics mirrored the apparent decay kinetics of the corresponding transcripts produced in transgenic plants under the control of a regulated promoter (Cab-1). The model system was then used to measure the decay rates of GUS reporter transcripts containing copies of the DST sequence inserted into the 3'UTR. An unmodified CAT gene introduced on the same vector served as the internal reference. These experiments and a parallel set utilizing a beta-globin reporter gene demonstrated that a synthetic dimer of the DST sequence was sufficient to destabilize both reporter transcripts in stably transformed tobacco cells. The decrease in transcript stability caused by the DST sequences in cultured cells was paralleled by a coordinate decrease in transcript abundance in transgenic tobacco plants. The implications of these results for the potential function of DST sequences within the SAUR transcripts are discussed.
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PMID:DST sequences, highly conserved among plant SAUR genes, target reporter transcripts for rapid decay in tobacco. 832