Nuclear localization of senescence marker protein-30, SMP30, in cultured mouse hepatocytes and its similarity to RNA polymerase.

Senescence marker protein-30 (SMP30), expressed mostly in the liver, protects cells against various injuries by stimulating membrane calcium-pump activity. By immunohistochemistry and western blotting, we found that SMP30 was in both the nuclei and cytoplasm of cultured mouse hepatocytes. By a homology search, we found that a domain of the SMP30 sequence 51 amino acid residues long was 60-66% similar to bacterial and yeast RNA polymerases.