Disease relevance of MGC76139

• Molecular cloning of Xenopus fibrillarin, a conserved U3 small nuclear ribonucleoprotein recognized by antisera from humans with autoimmune disease [1].

High impact information on MGC76139

• Although hypermethylation of the 5' cap of U8 RNA and fibrillarin binding can occur in either the cytoplasmic or nuclear compartment of Xenopus oocytes, neither is required for nuclear import [2].
• We isolated a 1.6-kilobase cDNA encoding fibrillarin from a Xenopus laevis cDNA library [1].
• Fibrillarin mRNA is accumulated early in oogenesis, like many other messengers, and translated during oocyte growth [3].
• Sections of the same oocytes, stained with a monoclonal antibody against nucleolar fibrillarin and anti-alphaIIsigma*, showed co-localisation of the two antibodies [4].
• By comparison, nucleolar remnants of adult chicken nucleated red blood cells contained only trace amounts of fibrillarin and NOR silver staining, whereas red blood cell nucleolar remnants of immature chicks had easily detectable amounts of fibrillarin and NOR silver staining [5].

Biological context of MGC76139

• In order to gain further insights into the fundamental structure of the nucleolus, nucleolar remnants of Xenopus and chickens were examined for the presence of fibrillarin and nucleolus organizer region (NOR) silver staining [5].
• Xenopus U14 is, therefore, a Box C/D fibrillarin-associated snoRNA that is required for site-specific 2'-O-ribose methylation of pre-rRNA [6].
• It is proposed that U3 and U14 snoRNA and fibrillarin, but not U8 snoRNA, bind to the external transcribed spacer or internal transcribed spacer 1, and when these binding sites are lost after actinomycin D treatment some of these components cannot be retained in the nucleolus [7].
• Fibrillarin and U3 RNA expression during Xenopus oogenesis and embryo development [8].
• Prenucleolar bodies in telophase/early interphase nuclei meet the definition of a pre-rRNA snurposome in that they contain U3 snoRNA and fibrillarin (and probably other processing components) but lack rDNA and do not synthesize rRNA [9].

Anatomical context of MGC76139

• Fibrillarin protein is thus progressively accumulated throughout oogenesis to be assembled with U3 snRNA and used for ribosome production in the amplified nucleoli [3].
• Nucleoli from hepatocytes of both adult and immature chickens demonstrated comparable levels of fibrillarin and NOR silver staining [5].
• Nucleolar remnants of Xenopus nucleated red blood cells were found to contain easily detectable amounts of fibrillarin and NOR silver staining [5].
• Since fibrillarin was found in nucleolar remnant structures, we tested for (and detected) its presence in residual nucleoli of in situ nuclear matrix derived from HeLa cells [5].

Associations of MGC76139 with chemical compounds

• Specifically, after most 40S, 38S and 36S pre-rRNAs have been depleted by incubation of Xenopus kidney cells in 0.05 microg/ml actinomycin D for 4 h, only 69% U3 small nucleolar RNA (snoRNA), 68% U14 snoRNA and 72% fibrillarin are retained in the nucleolus as compared with control cells [7].
• Immunofluorescence microscopy then tracked fibrillarin, nucleolin, and condensed DNA through oogenesis and into progesterone-induced meiotic maturation and nuclear breakdown [10].

Analytical, diagnostic and therapeutic context of MGC76139

• Immunoprecipitation experiments showed that the p40 protein corresponds to fibrillarin, indicating that this protein is intimately associated with the RNA [11].

References