Histone lysine ribosylation
Histone proteins often undergo ribosylation (ar) i.e. the addition of poly (ADP-ribose) units specifically at the lysine residues. This modification is mediated by Poly [ADP-ribose] polymerase (PARP) enzymes. In this case, the NAD+ acts as the ADP-ribose donor. These are big units and each ADP-ribose moiety adds ~560 Da to the histone protein. ADP-ribosylation causes disruption of the nucleosome structure by loss of histone-DNA interaction on account of charge modification.
ADP ribosylation plays an important role in DNA break repair mechanisms.
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| Site of modification | Writers | Erasers |
|---|---|---|
| H2AK13ar | Poly [ADP-ribose] polymerase 1 | |
| H2BK30ar | Poly [ADP-ribose] polymerase 1 | |
| H3K27ar | Poly [ADP-ribose] polymerase 1 | |
| H3K37ar | Poly [ADP-ribose] polymerase 1 | |
| H4K16ar | Poly [ADP-ribose] polymerase 1 |