The nuclear DEAD box RNA helicase p68 interacts with the nucleolar protein fibrillarin and colocalizes specifically in nascent nucleoli during telophase.
The DEAD box protein, p68, is an established RNA-dependent ATPase and RNA helicase in vitro, but neither the physiological function of this protein nor the macromolecules with which it interacts are known. Using a yeast two-hybrid screen, we identified the nucleolar protein, fibrillarin, as a protein that interacts with p68. Coimmunoprecipitation experiments confirmed that p68 and fibrillarin can form complexes in cellular extracts, and deletion analysis identified regions in each protein responsible for mediating the interaction. Immunofluorescence studies using confocal microscopy revealed that, in interphase cells, while fibrillarin is predominantly nucleolar, p68 shows a diffuse granular nuclear staining but is largely excluded from the nucleoli. Strikingly, both proteins colocalize in nascent nucleoli during late telophase. These data are consistent with a role for p68 either in postmitotic nucleolar reassembly or in the activation of ribosomal DNA transcription/preribosomal RNA processing during telophase and suggest that differential subnuclear compartmentalization may be a mechanism by which interaction of p68 with fibrillarin is regulated in the cell.
Nicol
S M
SM
Department of Molecular and Cellular Pathology, University of Dundee, Ninewells Medical School, Dundee, DD1 9SY.
Causevic
M
M
Prescott
A R
AR
Fuller-Pace
F V
FV
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002466:Cell Nucleolus / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000302:isolation & purification / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D013692:Telophase
D002868:Chromosomal Proteins, Non-Histone; D009687:Nuclear Proteins; C047458:fibrillarin; D011494:Protein Kinases; D000251:Adenosine Triphosphatases; C506749:Ddx5 protein, human; C506751:Ddx5 protein, mouse; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases