Architectural role for BCL6

Nuclear BTB/POZ proteins are often concentrated into discrete nuclear subdomains, but the role of these nuclear compartments is unclear. The BCL6 proto-oncogene, frequently altered in non-Hodgkin lymphoma, encodes a POZ/zinc finger protein that shows a characteristic localization in nuclear aggregates. In the November Molecular and Cellular Biology Albagli et al. used a tetracycline-regulated, epitope-tagged BCL6 allele to explore the significance of BCL6 aggregates (Mol Cell Biol 2000, 20:8560-8570). They employed pulse-labeling with bromodeoxyuridine (BrdU) together with electron- and laser-scanning confocal microscopy to determine the relationship between BCL6 expression and DNA replication. Electron microscopy showed that BCL6 is associated with early, mid and late replication foci during S phase. Careful ultrastructural analysis revealed that newly synthesised DNA appears wrapped around the BCL aggregates. Albagli et al. propose that BCL6 recruits chromatin-regulating proteins to nuclear subdomains, providing an organisation structure for the replication apparatus.