Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Estrogen-mediated accumulation of the avian apolipoprotein (apo) II mRNA is in part due to its stabilization. To identify the biochemical activity responsible for this effect, radiolabeled, capped, and polyadenylated apoII mRNA was incubated in vitro in liver cytosolic extracts from roosters who received either estrogen (estrogen-treated extract) or the vehicle (control extract) parenterally. The mRNA was very stable in estrogen-treated extract but was rapidly degraded in control extract. The RNA was degraded predominantly by endonuclease rather than exonuclease activity. The addition of the estrogen-treated extract to the control extract prevented the degradation of the mRNA in trans. This biochemical activity was heat labile and was also destroyed by proteinase K but not by micrococcal nuclease, indicating that estrogen treatment resulted in the expression of a protein in the liver that stabilized the apoII mRNA by inhibiting its nucleolytic degradation. This mRNA stabilization factor was labile around 60 degrees C, whereas the RNase remained stable up to 80 degrees C. Studies on mRNA protein interaction showed that both control and estrogen-treated extracts contain mRNA-binding (mRNP) proteins that bind apoII mRNA. An increased binding to apoII mRNA by a subset of these proteins was observed with estrogen-treated extract as compared with the control extract. This activity, although it afforded complete protection from nucleolytic degradation to apoII and apo A1 mRNAs, appeared to provide less protection to mRNAs encoding chicken serum albumin and vitellogenin, suggesting differential stabilization of mRNAs. These studies indicate that a cytosolic mRNA-stabilization factor, providing apoII mRNA complete protection from nucleolytic degradation, is expressed in the avian liver upon estrogen treatment. This appears to be the first time that a biochemical activity responsible for hormone-mediated stabilization of mRNAs and estrogen induction of mRNA binding by specific mRNPs have been identified and partially characterized in vitro.
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PMID:In vitro characterization of an estrogen-regulated mRNA stabilizing activity in the avian liver. 877 38

The editing of apolipoprotein-B (apoB) mRNA involves the deamination of cytidine at nucleotide 6666 to uridine. The catalytic subunit of the editing enzyme, apobec-1, is a cytidine deaminase that requires other unidentified proteins to edit apoB mRNA in vitro. We partially purified an activity from baboon kidney that functionally complements apobec-1. The complementing activity was protease-sensitive and micrococcal nuclease-resistant, had a native molecular mass of 65 +/- 10 kDa on size exclusion chromatography, and sedimented at 4.5 S in glycerol gradients. Purified recombinant His6-tagged apobec-1 immobilized on beads depleted >90% of the complementing activity from partially purified extracts. These beads edited apoB mRNA in vitro in the absence of exogenous apobec-1 or complementing activity. A functional holoenzyme containing apobec-1 and the complementing activity was eluted from the apobec-1-affinity resin using 0.5 M imidazole, whereas buffer containing 0.4 M KCl eluted only the complementing activity. The carboxyl-terminal 59 amino acids of apobec-1 were not required for interaction with the complementing activity in vitro. Our results demonstrate that the complementing protein interacts directly with apobec-1 in the absence of apoB mRNA.
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PMID:Apobec-1 interacts with a 65-kDa complementing protein to edit apolipoprotein-B mRNA in vitro. 891 Apr 49

An mRNA-dependent cell-free system has been developed from HepG2 cells by hydrolysis of endogenous mRNA with micrococcal nuclease. When supplied with RNA extracted from HepG2 cells, the system synthesized liver specific proteins such as albumin and apolipoprotein B100. Significant amounts of microsomes were also detected in the lysate by measuring NADH-cytochrome c reductase activity and ultracentrifugation. Protease protection assays showed the capability of the HepG2 lysate to translocate newly-synthesized proteins such as apolipoprotein Al, albumin, and apoB into the microsomes as they were protected from digestion with exogenously added protease K, but not protected in the presence of protease K and Triton X-100. The system also proved to be very active toward translation of exogenous mRNAs as evidenced by efficient translation of brome mosaic virus RNA. The HepG2 translation-translocation system appears to provide a unique homologous system for studies on the biogenesis of liver specific proteins, particulary apoB100.
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PMID:In vitro translation and translocation of apolipoprotein B in a cell-free system from HepG2 cells. 894 65