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. Localized predomintly in the nucleolus. Translocates from the nucleolus to the nucleoplasm upon apoptosis induction. Up-regulated by p53/TP53 in response to ionizing radiation and DNA-damaging agents such as adriamycin. Phosphorylation of p53/TP53 at 'Ser-15' is required for effective induction. Truncated N-terminus. Truncated N-terminus.