We have screened a human cDNA expression library in λgt11 for clones encoding Alu-binding proteins using direct binding of labeled Alu DNA to recombinant phage lysates fixed on a membrane, and isolated a clone 98% identical in sequence to the well-known substrate of protein kinases, annexin II, which was suggested earlier to play a role in transduction of mitogenic signals and DNA replication. A diagnostic property of annexins is their binding to phospholipids in the presence of calcium ions, and we have found that the interaction of proteins of human nuclear extracts with Alu subsequences is suppressed by Ca/phosphatidylserine liposomes, suggesting overlapping of Ca/phospholipid- and DNA-binding domains in annexin II.
