SUMO1 and cardiac hypertrophy: The major novel findings of the present study include: (1) PARP1 directly interacts with C/EBPβ and induce PARylation of C/EBPβ at K134 site in a conserved domain; (2) The accumulation of PARylation of C/EBPβ at K134 site exhibits downregulation of C/EBPβ SUMOylation at the same site and results in upregulation of C/EBPβ protein stability; (3) SUMO1 participates in PARP1-induced cardiac hypertrophy, which depends on SUMOylation at K134 site and protein level of C/EBPβ.