Exonuclease with activity against single- and double-stranded DNA and RNA. Mediates p53-induced apoptosis. When induced by p53 following DNA damage, digests double-stranded DNA to form single-stranded DNA and amplifies DNA damage signals, leading to enhancement of apoptosis (By similarity). Localized predomintly in the nucleolus. Translocates from the nucleolus to the nucleoplasm upon apoptosis induction (By similarity).