Sp100 nuclear antigen

Sp100 and nuclear dots

Two proteins, Sp100 and promyelocytic leukemia (PML) factor are localized to punctate domains in the nucleus (nuclear dots or nuclear bodies). These domains (few to 20) were found to form a donut-shaped structure when cells were starved of amino acids. In particular, deprivation of cystine results in most pronounced changes. Two other proteins, PIC1/SUMO-1, that also interact with nuclear pore complex factors also interact with these two proteins. In addition Sp100 interacts with a chromatin binding protein, HP1 alpha.

Sp100 splicoforms

Some Sp100 variants contain a domain similar to two interferon-inducible nuclear phosphoproteins, suppressin and DEAF1. This defines a novel protein motif, the HNPP-box. Another class of variants has high mobility group 1 (HMG1) protein sequence as a domain. Both major classes of Sp100 splice variant proteins localize in part to nuclear dots/PML bodies and other nuclear domains.

References

References

1. (1990). "Isolation and characterization of cDNA encoding a human nuclear antigen predominantly recognized by autoantibodies from patients with primary biliary cirrhosis". J. Immunol..
2. (1992). "IFN enhance expression of Sp100, an autoantigen in primary biliary cirrhosis". J. Immunol..
3. Kamei H. (1997). "Cystine starvation induces reversible large-body formation from nuclear bodies in T24 cells". Exp. Cell Res..
4. (1997). "Evidence for covalent modification of the nuclear dot-associated proteins PML and Sp100 by PIC1/SUMO-1". J. Cell Biol..
5. (1998). "Interaction of SP100 with HP1 proteins: a link between the promyelocytic leukemia-associated nuclear bodies and the chromatin compartment". Proc. Natl. Acad. Sci. U.S.A..
6. (1999). "Splice variants of the nuclear dot-associated Sp100 protein contain homologies to HMG-1 and a human nuclear phosphoprotein-box motif". J. Cell Sci..