Abstract. The nuclear domain (ND)10 also described as POD or Kr bodies is involved in the development of acute promyelocytic leukemia and virus-host interactions. Immunofluorescence analysis using a variety of human autoimmune sera and monoclonal antibodies showed a typical dot like nuclear staining for ND10, suggesting that this structure consists of several proteins. Two of the ND10 proteins, Spl00 and PML are genetically characterized and show homology with several transcription factors.Here we describe NDP52, an additional novel protein of the ND10. We raised a new mAb C8A2, that specifically recognizes NDP52. Immunofluorescence analysis using this mAb showed a typical nuclear dot staining as it was described for ND10. Isolation and sequencing of the corresponding cDNA revealed that NDP52 has a predicted molecular mass of 52 kD. The deduced amino acid sequence exhibits an extended central coiled coil domain containing a leucine zipper motif. The COOH terminus of NDP52 shows homology with LIM domains, that have recently been described to mediate protein interactions, which let NDP52 appear as a suitable candidate for mediating interactions between ND10 proteins. In vivo, NDP52 is transcribed in all human tissues analyzed. Furthermore, we show that NDP52 colocalizes with the ND10 protein PML and can be redistributed upon viral infection and interferon treatment. These data suggest that ND10 proteins play an important role in the viral life cycle. T HE internal structure and the role of the different organelles of the nucleus are less well characterized than those of the cytoplasm. Immunohistochemical studies and ultrastructural analyses have identified a number of nuclear domains, the components and functions of which are only partially understood. These structures include perichromatin fibrils, interchromatin granules and nuclear bodies (Fakan et al., 1984;Puvion et al., 1984;Visa et al., 1993). Some of the nuclear domains appear in a speckled or dot-like distribution within the nucleus. The components of the splicing regions, i.e., SC35 (Fu and Maniatis, 1990), hnRNPs (Fakan et al., 1984), and snRNPs (Spector et al., 1983), are concentrated in 20-50 nuclear speckles. The distribution of these speckles varies among different cell types and can be altered by several factors affecting transcription (Antoniou et al., 1993) and by virus infection (Bridge et al., 1993). ND10 are nuclear domains, originally characterized using mAbs and human autoantisera from patients with primary biliary cirrhosis. At the immunohistochemical level ND10 appear as nuclear dots, where 10 indicates the approximate number of dots observed per nucleus (Ascoli and Maul, 1991). ND10 did not colocalize with kinetochores, centromeres, sites of mRNA processing, and chromosomes. Resistance of ND10 antigens to nuclease digestion and salt extraction suggested that ND10 are associated with the nuclear matrix (Ascoli and Maul, 1991). Infection of ND10 positive cells with herpes simplex virus type-1 (HSV-1) 1 abrogates immunofluorescent staining o...
