SNM1B, or DNA cross-link repair 1B, is a human gene encoded by DCLRE1B. It may also be known as: 5' exonuclease Apollo; DNA cross-link repair 1B protein; SNM1 homolog B; SNMIB; hSNM1B; 5' exonuclease Apollo ; APOLLO. The encoded protein is an enzyme with an amino acid length of 532 and a mass of 60.0 kDa. Other isoforms may exist. SNM1B is a member of the DNA repair metallo-beta-lactamase (DRMBL) family. Homologs of this gene exist in other organisms, including: Mouse, Rat, Zebrafish, Frog, Chicken.