Changes of the nucleolus architecture in absence of the nuclear factor CTCF.

CTCF is a multifunctional nuclear factor involved in many cellular processes like gene regulation, chromatin insulation and genomic organization. Recently, CTCF has been shown to be involved in the transcriptional regulation of ribosomal genes and nucleolar organization in Drosophila cells and different murine cell types, including embryonic stem cells. Moreover, it has been suggested that CTCF could be associated to the nucleolus of human erythroleukemic K562 cells. In the present work, we took advantage of efficient small hairpin RNA interference against human CTCF to analyze nucleolar organization in HeLa cells. We have found that key components of the nucleolar architecture are altered. As a consequence of such alterations, an upregulation of ribosomal gene transcription was observed. We propose that CTCF contributes to the structural organization of the nucleolus and, through epigenetic mechanisms, to the regulation of the ribosomal gene expression.