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)

Autoimmune serum from a patient with scleroderma was shown by indirect immunofluorescence to label nucleoli in a variety of cells tested including: rat kangaroo PtK2, Xenopus A6, 3T3, HeLa, and human peripheral blood lymphocytes. Immunoblot analysis of nucleolar proteins with the scleroderma antibody resulted in the labeling of a single protein band of 34 kD molecular weight with a pI of 8.5. Electron microscopic immunocytochemistry demonstrated that the protein recognized by the scleroderma antiserum was localized exclusively in the fibrillar region of the nucleolus which included both dense fibrillar and fibrillar center regions. Therefore, we have named this protein "fibrillarin". Fibrillarin was found on putative chromosomal nucleolar organizer regions (NORs) in metaphase and anaphase, and during telophase fibrillarin was found to be an early marker for the site of formation of the newly forming nucleolus. Double label indirect immunofluorescence and immunoelectron microscopy on normal, actinomycin D-segregated, and DRB-treated nucleoli showed that fibrillarin and nucleolar protein B23 were predominantly localized to the fibrillar and granular regions of the nucleolus, respectively. RNase A and DNase I digestion of cells in situ demonstrated that fibrillarin was partially removed by RNase and completely removed by DNase. These results suggest that fibrillarin is a widely occurring basic nonhistone nucleolar protein whose location and nuclease sensitivity may indicate some structural and/or functional role in the rDNA-containing dense fibrillar and fibrillar center regions of the nucleolus.
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PMID:Fibrillarin: a new protein of the nucleolus identified by autoimmune sera. 293 2

Specific aims were to characterize the onset of nucleolar and extranucleolar transcription and expression of the nucleolar protein fibrillarin during preimplantation development in vitro in macaque embryos using autoradiographic and immunocytochemical techniques. Autoradiography was performed on whole embryos cultured with [3H]uridine for assessment of nucleolar (rRNA) and extranucleolar (mRNA) transcription. Expression of fibrillarin was immunocytochemically assessed in whole embryos using a primary antibody against fibrillarin and a fluorescein isothiocyanate-conjugated secondary antibody. Extranucleolar incorporation of [3H]uridine was first detected in 2-cell embryos cultured 6-10 h with [3H]uridine. Culture with alpha-amanitin prevented incorporation of label in 2-cell embryos, and treatment with ribonuclease reduced the signal to background levels, indicating that [3H]uridine was incorporated into mRNA and not rRNA or DNA. Nucleolar incorporation of [3H]uridine was not evident in pronucleate-stage or 2- to 5-cell embryos, but it was detected in one 6-cell embryo and in all 8-cell to blastocyst-stage embryos. Fibrillarin was first expressed in some 6- to 7-cell embryos, but it was consistently expressed in all 8-cell embryos. Fibrillarin was localized to the perimeter of the nucleolar precursor bodies, forming a ring that completely encapsulated these structures. Fibrillarin was not expressed in 8- to 16-cell embryos cultured with alpha-amanitin, indicating that it is transcribed, rather than recruited, at the 8-cell stage. In conclusion, in in vitro-fertilized macaque embryos developing in vitro, extranucleolar synthesis of mRNA is initiated at the 2-cell stage while the onset of nucleolar transcription occurs at the 6- to 8-cell stage, coincident with expression of fibrillarin.
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PMID:Onset of nucleolar and extranucleolar transcription and expression of fibrillarin in macaque embryos developing in vitro. 1002 22

Fibrillarin is one of the most important nucleolar proteins that have been shown as essential for life. Fibrillarin localizes primarily at the periphery between fibrillar center and dense fibrillar component as well as in Cajal bodies. In most plants there are at least two different genes for fibrillarin. In Arabidopsis thaliana both genes show high level of expression in transcriptionally active cells. Here, we focus on two important differences between A. thaliana fibrillarins. First and most relevant is the enzymatic activity by AtFib2. The AtFib2 shows a novel ribonuclease activity that is not seen with AtFib1. Second is a difference in the ability to interact with phosphoinositides and phosphatidic acid between both proteins. We also show that the novel ribonuclease activity as well as the phospholipid binding region of fibrillarin is confine to the GAR domain. The ribonuclease activity of fibrillarin reveals in this study represents a new role for this protein in rRNA processing.
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PMID:Novel Ribonuclease Activity Differs between Fibrillarins from Arabidopsis thaliana. 2916 3

Fibrillarin is a highly conserved nucleolar methyltransferase responsible for ribosomal RNA methylation across evolution from Archaea to humans. It has been reported that fibrillarin is involved in the methylation of histone H2A in nucleoli and other processes, including viral progression, cellular stress, nuclear shape, and cell cycle progression. We show that fibrillarin has an additional activity as a ribonuclease. The activity is affected by phosphoinositides and phosphatidic acid and insensitive to ribonuclease inhibitors. Furthermore, the presence of phosphatidic acid releases the fibrillarin-U3 snoRNA complex. We show that the ribonuclease activity localizes to the GAR (glycine/arginine-rich) domain conserved in a small group of RNA interacting proteins. The introduction of the GAR domain occurred in evolution in the transition from archaea to eukaryotic cells. The interaction of this domain with phospholipids may allow a phase separation of this protein in nucleoli.
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PMID:Fibrillarin Ribonuclease Activity is Dependent on the GAR Domain and Modulated by Phospholipids. 3238 86