Poly ADP-ribosylation of SET8 leads to aberrant H4K20 methylation domains in mammalian cells

In mammalian cells, SET8 mediated Histone H4 Lys 20 monomethylation (H4K20me1) has been implicated in regulating mitotic condensation, DNA replication, DNA damage response, and gene expression. Here we show SET8, the only known enzyme for H4K20me1 is post-translationally poly ADP-ribosylated by PARP1 on lysine residues. PARP1 interacts with SET8 in a cell cycle- dependent manner. Poly ADP-ribosylation on SET8 renders it catalytically compromised and it undergoes degradation via ubiquitylation pathway. Knockdown of PARP1 shifted the relative dynamic equilibrium of H4K20me2 to H4K20me3 in cells. Overexpression or knockdown of PARP1 led to aberrant H4K20me1 domains genome-wide, impacting Wnt signaling pathways genes and transcription factor binding site enrichment. Therefore, SET8 mediated chromatin remodeling in mammalian cells are influenced by poly ADP-ribosylation by PARP1. HeLa cells were grown according to ATCC's recommendations. PARP1 knockdown were performed in HeLa cells using esiRNA for 48hrs, esiRNA against GFP was used as control. PARP1 overexpression were performed using FLAG-PARP1 plasmid transfection in HeLa cells. ChIP seq libraries were made according to New England Biolabs's recommendations. Accessible chromatin labeling was done based on UniNicE-seq protocol and library for sequencing was generated based on One-pot Universal NicE-seq protocol.