Updated project metadata. The N-terminal three zinc finger motifs of PARP1 are evolutionarily conserved in multicellular organism。However, during apoptosis, human PARP1 is mainly cleaved by caspase 3 at D214. As a result, the truncated PARP1 loses two N-terminal zinc finger motifs and only contains the third zinc finger motif, the BRCT domain, the WGR domain and the C-terminal catalytic domain. Interestingly, when we explored the domain architecture of PARP1 in other organisms, we found that similar to human tPARP1, PARP1 orthologs in several lower organisms do not have the N-terminal two zinc fingers or even they lack the third zinc finger motif. It indicates that even without the first two zinc finger motifs, tPARP1 may still catalyze ADP-ribosylation and play an important role in certain biological processes. To reveal the biological function of tPARP1, we performed tandem affinity purification and searched for the possible substrates.