PML nuclear bodies (PML NBs) represent a nuclear domain originally described as an autoantigenic target in patient with primary biliary cirrhosis. They are now also known to play a role in pathogenesis of acute promyelocytic leukemia as well as in viral infection and possibly in proliferation control. About eleven different proteins have been localized in PML NBs so far, however, functional data are available only for two of the associated proteins : Sp100 protein and promyelocytic leukemia protein (PML).

Nuclear DNA helicase II (NDH II), alternatively named RNA helicase A, is a nuclear DNA/RNA helicase related to the Drosophila male dosage compensation factor mle. NDH II is the component of the Pol II holoenzyme which binds directly to CREB binding protein (CBP). This interaction is essential for CREB-dependent transcriptional activation in transfected cells in culture.

Here we report that NDH II was found to be a component of the PML nuclear bodies in cells treated with IFN-alpha. An autoimmune serum specific for PML NBs have been identified by screening of patient sera for those with an anti-nuclear antigen binding activity. NDH II was found to copurify specifically with PML NBs complexes after immunoprecipitation using G-protein Sepharose. Immunoflurescence studies showed that NDH II colocalizes with PML NBs after interferon stimulation, which microscopicaly confirmed our biochemical observations. Following transcriptional inhibition, NDH II was disassociated from PML NBs.

Our findings suggest that NDH II recruitment to PML NBs might be important for the role of this nuclear domain in transcriptional regulation and are consistent with the model that PML protein functions as a transcription factor.