Sp100 nuclear antigen (SP100)

Sp100 nuclear antigen is an interferon-induced nuclear protein, predominantly localized to punctate nuclear domains (known as nuclear dots or nuclear bodies) together with PML, participating in nuclear architecture, chromatin organization, and intrinsic cellular antiviral defense. It acts as an autoantigen in certain autoimmune liver diseases (notably primary biliary cirrhosis), with autoantibodies directed against SP100 serving as established clinical biomarkers. SP100 consists of several splice variants with differing C-terminal domains, including some harboring high-mobility group (HMG) and PHD finger/bromodomain motifs, suggesting roles in DNA binding and chromatin modification. SUMOylation of SP100 influences its localization and chromatin regulatory functions, with variants associating with both nuclear bodies and chromatin-rich domains. SP100 participates in transcriptional repression and gene regulation through interaction with heterochromatin protein HP1 and transcription factors such as ETS1 and p53. Its nuclear body localization and expression are increased by interferon signaling or environmental stress, and viral proteins may target SP100 to evade host cell intrinsic antiviral defenses. Disruption of nuclear bodies containing SP100 is associated with acute promyelocytic leukemia and certain neurodegenerative disorders.

Other names

Nuclear autoantigen Sp-100Nuclear dot-associated Sp100 proteinSpeckled 100 kDalysp100bSP100-HMG nuclear autoantigenSP100CSP100ASP100BSP100-HMG

Not applicable; no drugs are known to directly target SP100