PML nuclear bodies and their spatial relationships in the mammalian cell nucleus.

Promyelocytic leukaemia nuclear bodies (PML NBs) are found within the nucleus of mammalian cells, and are formed from the constituent proteins PML and Sp100. Numbering between 10 and 30 per cell, they are an obvious feature of the nuclear landscape, yet their functions have still to be unambiguously defined. In the mammalian nucleus, compartmentalization of functions is apparent, as reflected in the wide-range of other nuclear compartments that can be identified. These include nucleoli, transcription foci, splicing speckles, chromosomal topological markers such as centromeres and telomeres, the nuclear boundary, and the nucleoplasm itself. Quantification of the otherwise qualitative observations of relationships between mammalian nuclear compartments is essential for a complete understanding of nuclear processes. Here we describe some of the interesting known associations between PML NBs and other nuclear compartments, and comment upon their implications for PML NB function.