Poly(ADP-ribosylation)(PARylation)is apost-translational modification mediated by asubset of ADP-ribosyl transferases (ARTs). Although PARylation-inhibition based therapies areconsidered as an avenue to combat debilitating diseases such as cancerand myopathies, the roleof thismodificationinphysiological processes such ascell differentiation remainsunclear. Here we showthat Tankyrase1 (TNKS1), aPARylating ART, plays a major role in myogenesis, a vital process known to drivemuscle fiber formation and regeneration.Althoughallbona fidePARPs are expressed in muscle cells, experiments using siRNA-mediated knockdownor pharmacological inhibitionshow thatTKNS1 is the enzyme responsible ofcatalyzing PARylation during myogenesis. Via this activity,TKNS1controlsthe turnoverof mRNAs encoding myogenic regulatory factors such as nucleophosmin(NPM) and myogenin.TKNS1 mediates these effectsby targeting RNA-binding proteinssuch as Human Antigen R (HuR). HuR harbors a conserved TNKS-binding motif (TBM), the mutation of which not only prevents theassociation of HuR with TKNS1 anditsPARylation, but also precludes HuR from regulating the turnover of NPMand myogeninmRNAsas well as from promoting myogenesis. Therefore, our data uncovera new role forTNKS1as akeymodulator of RBP-mediated post transcriptionaleventsrequired for vitalprocesses suchasmyogenesis.