5'->3' double-stranded DNA exonuclease. Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding. By UV light, methyl methane-sulfonate (MMS) or hydroxyurea (HU), and during meiosis. Belongs to the XPG/RAD2 endonuclease family.