Mark O . J . Olson

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Mammalian cell nucleoli disassemble at the onset of M-phase and reassemble during telophase. Recent studies showed that partially processed preribosomal RNA (pre-rRNA) is preserved in association with processing components in the perichromosomal regions (PRs) and in particles called nucleolus-derived foci (NDF) during mitosis. Here, the dynamics of(More)
The cell nucleolus is the subnuclear body in which ribosomal subunits are assembled, and it is also the location of several processes not related to ribosome biogenesis. Recent studies have revealed that nucleolar components move about in a variety of ways. One class of movement is associated with ribosome assembly, which is a vectorial process originating(More)
The function of the nucleolus as a factory for assembling ribosomal subunits is well established, but many unrelated activities have been discovered over the past decade. Our understanding of the dynamics of nucleolar structure and its reassembly at the end of mitosis has recently advanced and the small nucleolar RNAs have been shown to be major players in(More)
Previous studies showed that components implicated in pre-rRNA processing, including U3 small nucleolar (sno)RNA, fibrillarin, nucleolin, and proteins B23 and p52, accumulate in perichromosomal regions and in numerous mitotic cytoplasmic particles, termed nucleolus-derived foci (NDF) between early anaphase and late telophase. The latter structures were(More)
Recent research suggests that the nucleolus communicates with the p53 regulatory system and acts as a stress sensor. Cellular stress causes nucleolar disruption, triggering the release of regulatory factors to the nucleoplasm. These factors, especially ARF (alternative reading frame), inhibit the degradation of p53, thereby facilitating its intracellular(More)
Protein B23 is a major nucleolar phosphoprotein proposed to be a ribosome assembly factor. Protein B23 exists as two isoforms, B23.1 and B23.2, differing only in their carboxyl-terminal sequences. The interaction of recombinantly produced B23 isoforms with double-stranded DNA was studied using gel retardation and nitrocellulose filter disk assays. Protein(More)
Protein B23 is a multifunctional nucleolar protein whose cellular location and characteristics strongly suggest that it is a ribosome assembly factor. The protein has nucleic acid binding, ribonuclease, and molecular chaperone activities. To determine the contributions of unique polypeptide segments enriched in certain classes of amino acid residues to the(More)
Nucleolin [C23 or 100 kilodaltons (kDa)] is the major nucleolar phosphorylated protein in exponentially growing Chinese hamster ovary cells. A nucleolar cyclic nucleotide independent protein kinase copurified with nucleolin in a complex which could be dissociated by hydroxyapatite chromatography. The kinase was stimulated by spermine and inhibited by(More)
The subcellular location of several nonribosomal nucleolar proteins was examined at various stages of mitosis in synchronized mammalian cell lines including HeLa, 3T3, COS-7 and HIV-1 Rev-expressing CMT3 cells. Nucleolar proteins B23, fibrillarin, nucleolin and p52 as well as U3 snoRNA were located partially in the peripheral regions of chromosomes from(More)
In earlier studies, the nucleolar levels of protein A24 were found to be markedly decreased in the nucleolar hypertrophy induced by thioacetamide or during liver regeneration (Ballal, N.R., Goldknopf, I.L., Goldberg, D.A., and Busch, H. (1974) Life Sci. 14, 1835-1845; Ballal, N.R., Kang, Y.-J., Olson, M.O.-J., and Busch, H.J. Biol. Chem. 250, 5921-5925). To(More)