EXPRESSION AND DNA-BINDING OF THE HUMAN 52-KDA RO SSA AUTOANTIGEN/

The 52 kDa Ro/SSA protein is an intracellular autoantigen that is freq uently recognized by antibodies in sera of patients with systemic lupu s erythematosus or Sjogren's syndrome. While the function of this mole cule is not known, zinc finger and leucine zipper motifs have been ide ntified in its predicted amino acid sequence which suggest that it may interact with nucleic acids. To test this hypothesis, the human gene which encodes this protein was cloned in a baculovirus and expressed i n Spodoptera frugipoda cells. Extracts from these infected insect cell s were used as a source of protein for this study, The protein is simi lar in size and antigenicity to that expressed in human cells. This pr otein binds to DNA at physiological temperature and is eluted with hig h concentrations of sodium chloride. Striking similarities were found between the sequence in, and adjacent to, the nucleic acid-binding mot ifs of 52 kDa Ro/SSA and a growing family of zinc finger proteins whic h have been shown to bind to DNA or regulate gene expression. The find ings presented here place this protein structurally and functionally i n this family and demonstrate a biochemical assay which can be used to study its function.