Melatonin regulates PARP1 to control the senescence‐associated secretory phenotype (SASP) in human fetal lung fibroblast cells

Cellular senescence is an important tumor-suppressive mechanism. However, acquisition of a senescence-associated secretory phenotype (SASP) in senescent cells has deleterious effects on the tissue microenvironment and, paradoxically, promotes tumor progression. In a drug screen, we identified melatonin as a novel SASP suppressor in human cells. Strikingly, melatonin blunts global SASP gene expression upon oncogene-induced senescence (OIS). Moreover, poly(ADP-ribose) polymerase-1 (PARP-1), a sensor of DNA damage, was identified as a new melatonin-dependent regulator of SASP gene induction upon OIS. Here, we report two different but potentially coherent epigenetic strategies for melatonin regulation of SASP. The interaction between the telomeric repeat-containing RNA (TERRA) and PARP-1 stimulates the SASP, which was attenuated by 67.9% (illustrated by the case of IL8) by treatment with melatonin. Through binding to macroH2A1.1, PARP-1 recruits CREB-binding protein (CBP) to mediate acetylation of H2BK120, which positively regulates the expression of target SASP genes, and this process is interrupted by melatonin. Consequently, the findings provide novel insight into melatonin's epigenetic role via modulating PARP-1 in suppression of SASP gene expression in OIS-induced senescent cells. Our studies identify melatonin as a novel anti-SASP molecule, define PARP-1 as a new target by which melatonin regulates SASP, and establish a new epigenetic paradigm for a pharmacological mechanism by which melatonin interrupts PARP-1 interaction with the telomeric long noncoding RNA(lncRNA) or chromatin.