A human gene coding for a membrane-associated nucleic acid-binding protein

Studies to clone a cell-surface DNA-binding protein involved in the binding and internalization of extracellular DNA have led to the isolation of a ge ne for a membrane-associated nucleic acid-binding protein (MNAB). The full- length cDNA is 4.3 kilobases with an open reading frame of 3576 base pairs encoding a protein of similar to 130 kDa (GenBank accession numbers AF25530 3 and AF255304), The MNAB gene is on human chromosome 9 with wide expressio n in normal tissues and tumor cells. A C3HC4 RING finger and a CCCH zinc fi nger have been identified in the amino-terminal half of the protein. MNAB b ound DNA (K-D similar to4 nM) and mutagenesis of a single conserved amino a cid in the zinc finger reduced DNA binding by 50%. A potential transmembran e domain exists near the carboxyl terminus, Antibodies against the amino te rminal half of the protein immunoprecipitated a protein of molecular mass s imilar to 150 kDa and reacted with cell surfaces. The MNAB protein is membr ane-associated and primarily localized to the perinuclear space, probably t o the endoplasmic reticulum or trans-Golgi network, Characterization of the MNAB protein as a cell-surface DNA-binding protein, critical in binding an d internalization of extracellular DNA, awaits confirmation of its localiza tion to cell surfaces.