Differential distribution of factors involved in pre-mRNA processing in the yeast cell nucleus

Cold Spring Harbor Laboratory, New York 11724.
Molecular and Cellular Biology (Impact Factor: 4.78). 08/1990; 10(7):3524-34. DOI: 10.1128/MCB.10.7.3524
Source: PubMed


The yeast cell nucleus has previously been shown to be divided into two regions by a variety of microscopic approaches. We
used antibodies specific for the 2,2,7-trimethylguanosine cap structure of small nuclear ribonucleic acids (snRNAs) and for
a protein component of small nuclear ribonucleoprotein particles to identify the distribution of small nuclear ribonucleoprotein
particles within the yeast cell nucleus. These studies were performed with the fission yeast Schizosaccharomyces pombe and
the budding yeast Saccharomyces cerevisiae. By using immunofluorescence microscopy and immunoelectron microscopy, most of
the abundant snRNAs were localized to the portion of the nucleus which has heretofore been referred to as the nucleolus. This
distribution of snRNAs is different from that found in mammalian cells and suggests that the nucleolar portion of the yeast
nucleus contains functional domains in addition to those associated with RNA polymerase I activity.

Download full-text


Available from: Judith A Potashkin
  • Source
    • "noRNAs ( Fig . 1b ) . This is in agreement with earlier findings that reported the presence of several U snRNPs within the mammalian nucleolus ( Ganot et al . 1999 ; Gerbi and Lange 2002 ; Lyon et al . 1997 ; Sleeman et al . 1998 ; Sleeman and Lamond 1999 ; Tycowski et al . 1998 ) as well as the presence of TMG - labelling in the yeast nucleolus ( Potashkin et al . 1990 ) . The INB appears totally enclosed within the nucleolus , as judged by fibrillarin or nucleolin co - staining , and therefore is not likely to be a nucleoplasmic invagination . Other nuclear proteins , such as RNA polymerase II , the SR protein SRp55 and topoisomerase II beta ( Fig . 1b and data not shown ) , are not detected within t"
    [Show abstract] [Hide abstract]
    ABSTRACT: The nucleolus is the subnuclear organelle responsible for ribosome subunit biogenesis and can also act as a stress sensor. It forms around clusters of ribosomal DNA (rDNA) and is mainly organised in three subcompartments, i.e. fibrillar centre, dense fibrillar component and granular component. Here, we describe the localisation of 21 protein factors to an intranucleolar region different to these main subcompartments, called the intranucleolar body (INB). These factors include proteins involved in DNA maintenance, protein turnover, RNA metabolism, chromatin organisation and the post-translational modifiers SUMO1 and SUMO2/3. Increase in the size and number of INBs is promoted by specific types of DNA damage and depends on the functional integrity of the nucleolus. INBs are abundant in nucleoli of unstressed cells during S phase and localise in close proximity to rDNA with heterochromatic features. The data suggest the INB is linked with regulation of rDNA transcription and/or maintenance of rDNA. Electronic supplementary material The online version of this article (doi:10.1007/s00412-011-0327-8) contains supplementary material, which is available to authorized users.
    Full-text · Article · Jun 2011 · Chromosoma
  • Source
    • "Interestingly, structures similar to nuclear speckles have been identified in the amphibian oocyte nucleus (Gall et al. 1999) and in Drosophila melanogaster embryos when transcription increases upon cellularization during cycle 14 (Segalat et al. 1992), but not in yeast (Potashkin et al. 1990). Importantly, not all nuclear proteins that show a speckle-like labeling pattern by immunofluorescence microscopy localize to IGCs. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Nuclear speckles, also known as interchromatin granule clusters, are nuclear domains enriched in pre-mRNA splicing factors, located in the interchromatin regions of the nucleoplasm of mammalian cells. When observed by immunofluorescence microscopy, they usually appear as 20-50 irregularly shaped structures that vary in size. Speckles are dynamic structures, and their constituents can exchange continuously with the nucleoplasm and other nuclear locations, including active transcription sites. Studies on the composition, structure, and dynamics of speckles have provided an important paradigm for understanding the functional organization of the nucleus and the dynamics of the gene expression machinery.
    Preview · Article · Oct 2010 · Cold Spring Harbor perspectives in biology
  • Source
    • "Phosphorylation of different serine residues within the RS domain may confer different activities or functions upon SR proteins or interactions with different partners and/or subnuclear compartments. This possibility is also supported by the finding that Schizosaccharomyces pombe contains only two SR proteins and nuclear speckles have not been observed in these cells (Potashkin et al., 1990), and no SR proteins are encoded in the Saccharomyces cerevisiae genome and once again no speckles have been identified in these cells (for review see Graveley, 2000). In mammalian cells, it is not clear how pre-mRNA processing factors are activated to a splicingcompetent state in newly forming nuclei that have not yet assembled nuclear speckles. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Upon completion of mitosis, daughter nuclei assemble all of the organelles necessary for the implementation of nuclear functions. We found that upon entry into daughter nuclei, snRNPs and SR proteins do not immediately colocalize in nuclear speckles. SR proteins accumulated in patches around active nucleolar organizing regions (NORs) that we refer to as NOR-associated patches (NAPs), whereas snRNPs were enriched at other nuclear regions. NAPs formed transiently, persisting for 15-20 min before dissipating as nuclear speckles began to form in G1. In the absence of RNA polymerase II transcription, NAPs increased in size and persisted for at least 2 h, with delayed localization of SR proteins to nuclear speckles. In addition, SR proteins in NAPs are hypophosphorylated, and the SR protein kinase Clk/STY colocalizes with SR proteins in NAPs, suggesting that phosphorylation releases SR proteins from NAPs and their initial target is transcription sites. This work demonstrates a previously unrecognized role of NAPs in splicing factor trafficking and nuclear speckle biogenesis.
    Full-text · Article · Nov 2004 · The Journal of Cell Biology
Show more