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Human PARP-1, PARP-2, and PARP-3 are key players in the cellular response to DNA damage, during which their catalytic activities are acutely stimulated through interaction with DNA strand breaks. There are also roles for these PARPs outside of the DNA damage response, most notably for PARP-1 and PARP-2 in the regulation of gene expression. Here, we describe a general method to express and purify these DNA damage-dependent PARPs from E. coli cells for use in biochemical assays and for structural and functional analysis. The procedure allows for robust production of PARP enzymes that are free of contaminant DNA that can interfere with downstream analysis. The described protocols have been updated from our earlier reported methods, most importantly to introduce PARP inhibitors in the production scheme to cope with enzyme toxicity that can compromise the yield of purified protein.

A general method to express and purify full-length human poly(ADP-ribose) polymerase-1 (PARP-1), individual PARP-1 domains, and groups of PARP-1 domains from Escherichia coli cells is described. The procedure allows for robust production of highly pure PARP-1 that is free of DNA contamination and well-suited for biochemical experiments and for structural and biophysical analysis. Two biochemical assays for monitoring PARP-1 automodification activity are presented that can be used to evaluate purified PARP-1, combinations of PARP-1 domains, or PARP-1 mutants.