TIP49, HOMOLOGOUS TO THE BACTERIAL-DNA HELICASE RUVB, ACTS AS AN AUTOANTIGEN IN HUMAN

TATA-binding protein (TBP), a central component for transcriptional re gulation, forms complexes with various transcription regulators. We ha ve isolated a novel human cDNA for a 49-kD TBP-interacting protein (TI P49). The human TIP49 was highly homologous to bacterial RuvB proteins that function as a DNA helicase to promote branch migration of the Ho lliday junction. Immunofluorescence analysis using anti-TIP49 antibody showed a typical dot-shaped nuclear staining pattern, suggesting that TIP49 is included in a macromolecular structure in the nucleus and ma y participate in nuclear events such as transcription and recombinatio n. Moreover, glycerol gradient analysis demonstrated that TIP49 is pre sent in a macromolecular complex in nuclear extracts. Interestingly, w e detected a high level of autoantibodies against TIP49 in sera of pat ients with autoimmune diseases such as polymyositis/dermatomyositis an d autoimmune hepatitis. This indicates that the autoantibody against t his protein is a new marker for particular connective tissue diseases. These findings provide further evidence that the macromolecular struc tures described above are targeted by an autoimmune mechanism. The ant i-TIP49 antibodies can be useful probes for clinical diagnosis and for investigation of intranuclear structure. (C) 1998 Academic Press.