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Title: Evidence for nucleolar subcompartments in Dictyostelium

Abstract

Highlights: • Two nucleolar subcompartments (NoSC1, NoSC2) were found in Dictyostelium. • Specific nucleolar proteins localize to different nucleolar subcompartments. • Specific proteins exit NoSC1 and NoSC2 differently upon Actinomycin D treatment. • KRKR appears to function as an NoSC2 nucleolar subcompartment localization signal. - Abstract: The nucleolus is a multifunctional nuclear compartment usually consisting of two to three subcompartments which represent stages of ribosomal biogenesis. It is linked to several human diseases including viral infections, cancer, and neurodegeneration. Dictyostelium is a model eukaryote for the study of fundamental biological processes as well as several human diseases however comparatively little is known about its nucleolus. Unlike most nucleoli it does not possess visible subcompartments at the ultrastructural level. Several recently identified nucleolar proteins in Dictyostelium leave the nucleolus after treatment with the rDNA transcription inhibitor actinomycin-D (AM-D). Different proteins exit in different ways, suggesting that previously unidentified nucleolar subcompartments may exist. The identification of nucleolar subcompartments would help to better understand the nucleolus in this model eukaryote. Here, we show that Dictyostelium nucleolar proteins nucleomorphin isoform NumA1 and Bud31 localize throughout the entire nucleolus while calcium-binding protein 4a localizes to only a portion, representing nucleolar subcompartment 1 (NoSC1). SWI/SNF complexmore » member Snf12 localizes to a smaller area within NoSC1 representing a second nucleolar subcompartment, NoSC2. The nuclear/nucleolar localization signal KRKR from Snf12 localized GFP to NoSC2, and thus also appears to function as a nucleolar subcompartment localization signal. FhkA localizes to the nucleolar periphery displaying a similar pattern to that of Hsp32. Similarities between the redistribution patterns of Dictyostelium nucleolar proteins during nucleolar disruption as a result of either AM-D treatment or mitosis support these subcompartments. A model for the AM-D-induced redistribution patterns is proposed.« less

Authors:
 [1];  [1];  [2]
  1. Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Rd. N., Mississauga, Ontario L5L 1C6 (Canada)
  2. (Canada)
Publication Date:
OSTI Identifier:
22416906
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 456; Journal Issue: 4; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ACTINOMYCIN; CALCIUM; HUMAN POPULATIONS; MITOSIS; NEOPLASMS; NUCLEOLI; PROTEINS; RIBOSOMAL RNA; TRANSCRIPTION

Citation Formats

Catalano, Andrew, E-mail: acatalano@ccny.cuny.edu, O’Day, Danton H., E-mail: danton.oday@utoronto.ca, and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario M5S 3G5. Evidence for nucleolar subcompartments in Dictyostelium. United States: N. p., 2015. Web. doi:10.1016/J.BBRC.2014.12.050.
Catalano, Andrew, E-mail: acatalano@ccny.cuny.edu, O’Day, Danton H., E-mail: danton.oday@utoronto.ca, & Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario M5S 3G5. Evidence for nucleolar subcompartments in Dictyostelium. United States. doi:10.1016/J.BBRC.2014.12.050.
Catalano, Andrew, E-mail: acatalano@ccny.cuny.edu, O’Day, Danton H., E-mail: danton.oday@utoronto.ca, and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario M5S 3G5. Sat . "Evidence for nucleolar subcompartments in Dictyostelium". United States. doi:10.1016/J.BBRC.2014.12.050.
@article{osti_22416906,
title = {Evidence for nucleolar subcompartments in Dictyostelium},
author = {Catalano, Andrew, E-mail: acatalano@ccny.cuny.edu and O’Day, Danton H., E-mail: danton.oday@utoronto.ca and Department of Cell and Systems Biology, University of Toronto, 25 Harbord St., Toronto, Ontario M5S 3G5},
abstractNote = {Highlights: • Two nucleolar subcompartments (NoSC1, NoSC2) were found in Dictyostelium. • Specific nucleolar proteins localize to different nucleolar subcompartments. • Specific proteins exit NoSC1 and NoSC2 differently upon Actinomycin D treatment. • KRKR appears to function as an NoSC2 nucleolar subcompartment localization signal. - Abstract: The nucleolus is a multifunctional nuclear compartment usually consisting of two to three subcompartments which represent stages of ribosomal biogenesis. It is linked to several human diseases including viral infections, cancer, and neurodegeneration. Dictyostelium is a model eukaryote for the study of fundamental biological processes as well as several human diseases however comparatively little is known about its nucleolus. Unlike most nucleoli it does not possess visible subcompartments at the ultrastructural level. Several recently identified nucleolar proteins in Dictyostelium leave the nucleolus after treatment with the rDNA transcription inhibitor actinomycin-D (AM-D). Different proteins exit in different ways, suggesting that previously unidentified nucleolar subcompartments may exist. The identification of nucleolar subcompartments would help to better understand the nucleolus in this model eukaryote. Here, we show that Dictyostelium nucleolar proteins nucleomorphin isoform NumA1 and Bud31 localize throughout the entire nucleolus while calcium-binding protein 4a localizes to only a portion, representing nucleolar subcompartment 1 (NoSC1). SWI/SNF complex member Snf12 localizes to a smaller area within NoSC1 representing a second nucleolar subcompartment, NoSC2. The nuclear/nucleolar localization signal KRKR from Snf12 localized GFP to NoSC2, and thus also appears to function as a nucleolar subcompartment localization signal. FhkA localizes to the nucleolar periphery displaying a similar pattern to that of Hsp32. Similarities between the redistribution patterns of Dictyostelium nucleolar proteins during nucleolar disruption as a result of either AM-D treatment or mitosis support these subcompartments. A model for the AM-D-induced redistribution patterns is proposed.},
doi = {10.1016/J.BBRC.2014.12.050},
journal = {Biochemical and Biophysical Research Communications},
number = 4,
volume = 456,
place = {United States},
year = {Sat Jan 24 00:00:00 EST 2015},
month = {Sat Jan 24 00:00:00 EST 2015}
}
  • The phosphorylated oligosaccharides of Dictyostelium discoideum contain methylphosphomannosyl residues which are stable to mild-acid and base hydrolysis. Evidence is presented that these methyl groups are derived from (methyl-/sup 3/H)methionine, in vivo and (methyl-/sup 3/H)S-adenosylmethionine in vitro. About 18% of the macromolecules secreted from vegetative cells labeled with (methyl-/sup 3/H)methionine are released by digestion with preparations of endoglycosidase/peptide N-glycosidase F. The majority of the released molecules are sulfated, anionic high mannose-type oligosaccharides. Strong acid hydrolysis of the (/sup 3/H)methyl-labeled molecules yields (/sup 3/H)methanol with kinetics of release similar to those found for the generation of Man-6-P from chemically synthesized methylphosphomannose methylglycoside.more » Treatment of the (/sup 3/H)methyl-labeled molecules with a phosphodiesterase from Aspergillus niger which is known to cleave this phosphodiester also releases (/sup 3/H)methanol from a portion of the oligosaccharides.« less
  • The authors describe the biochemical features of the putative cell cohesion molecule antigen 117, indicating that it is anchored to the plasma membrane by a glycolipid tail. Antigen 117 can be radiolabeled with ({sup 3}H)myristate, ({sup 3}H)palmitate, and ({sup 14}C)ethanolamine. The fatty acid label is removed by periodate oxidation and nitrous acid deamination, indicating that the fatty acid is attached to the protein by a structure containing carbohydrate and an unsubstituted glucosamine. As cells develop aggregation competence, the antigen is released from the cell surface in a soluble form that can still be radiolabeled with ({sup 14}C)ethanolamine but not withmore » ({sup 3}H)myristate of ({sup 3}H)-palmitate. The molecular weight of the released antigen is similar to that found in the plasma membrane, but it preferentially partitions in Triton X-114 as a hydrophilic, as opposed to a hydrophobic, protein. Plasma membranes contain the enzyme activity responsible for the release of the antigen in a soluble form.« less
  • Nop25 is a putative RNA binding nucleolar protein associated with rRNA transcription. The present study was undertaken to determine the mechanism of Nop25 localization in the nucleolus. Deletion experiments of Nop25 amino acid sequence showed Nop25 to contain a nuclear targeting sequence in the N-terminal and a nucleolar targeting sequence in the C-terminal. By expressing derivative peptides from the C-terminal as GFP-fusion proteins in the cells, a lysine and arginine residue-enriched peptide (KRKHPRRAQDSTKKPPSATRTSKTQRRRR) allowed a GFP-fusion protein to be transported and fully retained in the nucleolus. When the peptide was fused with cMyc epitope and expressed in the cells, amore » cMyc epitope was then detected in the nucleolus. Nop25 did not localize in the nucleolus by deletion of the peptide from Nop25. Furthermore, deletion of a subdomain (KRKHPRRAQ) in the peptide or amino acid substitution of lysine and arginine residues in the subdomain resulted in the loss of Nop25 nucleolar localization. These results suggest that the lysine and arginine residue-enriched peptide is the most prominent nucleolar targeting sequence of Nop25 and that the long stretch of basic residues might play an important role in the nucleolar localization of Nop25. Although Nop25 contained putative SUMOylation, phosphorylation and glycosylation sites, the amino acid substitution in these sites had no effect on the nucleolar localization, thus suggesting that these post-translational modifications did not contribute to the localization of Nop25 in the nucleolus. The treatment of the cells, which expressed a GFP-fusion protein with a nucleolar targeting sequence of Nop25, with RNase A resulted in a complete dislocation of the protein from the nucleolus. These data suggested that the nucleolar targeting sequence might therefore play an important role in the binding of Nop25 to RNA molecules and that the RNA binding of Nop25 might be essential for the nucleolar localization of Nop25.« less