In this issue of Genes & Development, Grob and colleagues (pp. 220-230) identify the minimal molecular requirements to assemble a fully functional nucleolus in human cells and demonstrate the importance of the nucleolar transcription factor upstream binding factor (UBF) as a mitotic bookmark at the ribosomal DNA (rDNA).
Keywords: UBF; mitotic bookmarking; neo-NOR; nucleolar organizer region (NOR); nucleolus; pseudo-NOR.