This domain, known as the Pseudo-exo domain, is found DNA polymerase Nu protein in species such as Homo sapiens. Residues 192-416 of Pol nu formed a degenerate 3'-5'-exonuclease domain, which deviates from the equivalent [1].

1: How a homolog of high-fidelity replicases conducts mutagenic DNA synthesis. Lee YS, Gao Y, Yang W; Nat Struct Mol Biol. 2015;22:298-303. PMID:25775266