Cloning and characterization of a full length cDNA encoding Sp110 (speckled 110), a novel 110 kDa polypeptide, is disclosed. It is disclosed that Sp110 is a component of the nuclear body, is expressed in leukocytes, and is also expressed in other types of cells, including endothelial cells, smooth muscle cells, liver cells and heart cells, after contact with certain cytokines. The disclosure also includes the following: Sp140 recruits Sp110 to the nuclear body, Sp110 functions as an activator of gene transcription, and Sp110 serves as a nuclear hormone receptor co-activator. Sp110 DNAs, polypeptides, antibodies are disclosed. Also disclosed are Sp110-related screening methods and clinical diagnostic methods.