Cell-specific nucleolar localization of TBP-related factor 2.
TATA-binding protein (TBP)-related factor 2 (TRF2) is one of four closely related RNA polymerase II transcription factors. We compared the intracellular localizations of TBP and TRF2 during the cell cycle and mitosis in HeLa cells. We show that during interphase, endogenous or exogenously expressed TRF2 is located almost exclusively in the nucleolus in HeLa or Cos cells. TRF2 localization is not affected by stress or mitotic stimuli, but TRF2 is rapidly released from the nucleolus upon inhibition of pol I transcription or treatment by RNase. These results suggest that localization of HeLa TRF2 requires a nucleolar-associated RNA species. In contrast, in 3T3 fibroblast cells, exogenously expressed TRF2 localizes to the nucleoplasm. Constitutive expression of ectopic TRF2 in 3T3 cells leads to a prolonged S phase of the cell cycle and reduced proliferation. Together with previous data, our results highlight the cell-specific localization and functions of TRF2. Furthermore, we show that during cell division, HeLa TRF2 and TBP are localized in the mitotic cytoplasm and TRF2 relocalizes into the nascent nucleoli immediately after mitosis, whereas TBP reassociates with the chromatin. Although partially contradictory results have been reported, our data are consistent with a model where only small proportion of the cellular TBP remains associated with specific promoter loci during mitosis.
Kieffer-Kwon
Philippe
P
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, 67404 Illkirch Cédex, France.
Martianov
Igor
I
Davidson
Irwin
I
D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002453:Cell Cycle / Q000502:physiology*; D002466:Cell Nucleolus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004256:DNA Polymerase I / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D035182:TATA Box Binding Protein-Like Proteins / Q000378:metabolism*; D035181:TATA-Box Binding Protein / Q000378:metabolism; D035341:Telomeric Repeat Binding Protein 2; D014158:Transcription, Genetic
D009687:Nuclear Proteins; D035182:TATA Box Binding Protein-Like Proteins; D035181:TATA-Box Binding Protein; C504753:TERF2 protein, human; D035341:Telomeric Repeat Binding Protein 2; D004256:DNA Polymerase I