Table S1.

Caspase 3 cleaves Pax7 at aspartic acid D187

Start to end	Sequence	Interpretation
188–208	D.GILGDKGMRLDEGSDVESEPD.L	Caspase plus GluC
188–211	D.GILGDKGMRLDEGSDVESEPDLPL.K	Caspase plus chymotrypsin
188–213	D.GILGDKGMRLDEGSDVESEPDLPLKR.K	Caspase plus trypsin
188–214	D.GILGDKGMRLDEGSDVESEPDLPLKRK.Q	Caspase plus trypsin
188–215	D.GILGDKGMRLDEGSDVESEPDLPLKRKQ.R	Caspase plus GluC
188–216	D.GILGDKGMRLDEGSDVESEPDLPLKRKQR.R	Caspase plus trypsin

Recombinant Pax7 was subjected to an in vitro caspase 3 cleavage assay and directly processed for LC-MS/MS and MASCOT software was used to analyze and identify peptides mapping to the Pax7 protein. The peptides identified were queried for cleavage events following an aspartic acid residues which could not be attributed to cleavage via one of the endoproteases used for LC-MS/MS processing. The resultant peptides, listed, all identified a site at D187, which identifies it as a caspase 3 cleavage site.