Disconnection between rDNA transcription sites and the late rRNA processing proteins can be induced either by kinase inhibitors or by modiWcations of snoRNA domains (Chan et al. 1996; Colau et al. 2004; David-Pfeuty et al. 2001; Rubbi and Milner 2003; Sirri et al. 2002) . The separation of the DFC and GC can be reversed by removal of a CK2 inhibitor, restoring nucleolar organization. The CK2 kinase is known to phosphorylate several nucleolar proteins (Meggio and Pinna 2003) . We postulate that the connection between DFC and GC is controlled at least in part by phosphorylation of these proteins. This hypothesis was veriWed for B23 by mutation of the major site of CK2 phosphorylation (Louvet et al. 2006 ). In conclusion, the rRNA processing proteins can be disconnected from the rRNA transcription sites indicating that rRNA transcripts are not suYcient to attract the processing proteins in these conditions. The dynamics of nucleolar reformation and the connection between DFC and GC is ATP/GTP dependent, sensitive to temperature, and is CK2-driven.