PARP1 and medulloblastoma: Thus, not only apoptosis but also senescence may be involved in the synthetic lethality interactions in vivo. This was verified for the first time between genes encoding the DNA repair and recombination protein RAD54-like (Rad54) essential for homologous recombination (HR) and the poly(ADP-ribose) polymerase 1 (PARP1) responsible for DNA repair in Ptc1 heterozygous mice with developed medulloblastoma.