Targeting of CTCF to the nucleolus inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism.
Multiple functions have been reported for the transcription factor and candidate tumour suppressor, CTCF. Among others, they include regulation of cell growth, differentiation and apoptosis, enhancer-blocking activity and control of imprinted genes. CTCF is usually localized in the nucleus and its subcellular distribution during the cell cycle is dynamic; CTCF was found associated with mitotic chromosomes and the midbody, suggesting different roles for CTCF at different stages of the cell cycle. Here we report the nucleolar localization of CTCF in several experimental model systems. Translocation of CTCF from nucleoplasm to the nucleolus was observed after differentiation of K562 myeloid cells and induction of apoptosis in MCF7 breast cancer cells. CTCF was also found in the nucleoli in terminally differentiated rat trigeminal ganglion neurons. Thus our data show that nucleolar localization of CTCF is associated with growth arrest. Interestingly, the 180 kDa poly(ADP-ribosyl)ated isoform of CTCF was predominantly found in the nucleoli fractions. By transfecting different CTCF deletion constructs into cell lines of different origin we demonstrate that the central zinc-finger domain of CTCF is the region responsible for nucleolar targeting. Analysis of subnucleolar localization of CTCF revealed that it is distributed homogeneously in both dense fibrillar and granular components of the nucleolus, but is not associated with fibrillar centres. RNA polymerase I transcription and protein synthesis were required to sustain nucleolar localization of CTCF. Notably, the labelling of active transcription sites by in situ run-on assays demonstrated that CTCF inhibits nucleolar transcription through a poly(ADP-ribosyl)ation-dependent mechanism.
Torrano
Verónica
V
Grupo de Biología Molecular del Cáncer, Departamento de Biologia Molecular, Universidad de Cantabria, 39011-Santander, Spain.
Navascués
Joaquín
J
Docquier
France
F
Zhang
Ru
R
Burke
Les J
LJ
Chernukhin
Igor
I
Farrar
Dawn
D
León
Javier
J
Berciano
María T
MT
Renkawitz
Rainer
R
Klenova
Elena
E
Lafarga
Miguel
M
Delgado
M Dolores
MD
D000818:Animals; D000076246:CCCTC-Binding Factor; D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D021382:Protein Sorting Signals; D021381:Protein Transport / Q000502:physiology; D011506:Proteins / Q000378:metabolism*; D012318:RNA Polymerase I / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D012668:Trigeminal Ganglion / Q000166:cytology; D016335:Zinc Fingers
D000076246:CCCTC-Binding Factor; C000619697:CTCF protein, human; D004268:DNA-Binding Proteins; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D021382:Protein Sorting Signals; D011506:Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C024857:poly(ADP)-ribosylated proteins; D011064:Poly Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D012318:RNA Polymerase I