Coilin and SUMOylation influence PARP1 dynamics and the DNA damage response.

Coilin is a nucleoplasmic protein that is enriched in some cell types in the Cajal body (CB). CBs take part in the biogenesis of many different types of ribonucleoproteins (RNPs), such as small nuclear RNPs. Coilin is known as the CB marker protein and is required for CB formation. The function of nucleoplasmic coilin is less understood and has been shown to impact protein modification by SUMO, the small ubiquitin-like modifier. Additionally, it is known that coilin is recruited to sites of DNA damage caused by UVA exposure or expression of herpes simplex viral protein. PARP1, a DNA damage response protein, has been shown to be SUMOylated by PIAS4, a SUMO E3 ligase that associates with coilin. Here, we show that SUMOylation of PARP1 is lessened when coilin is suppressed. We also found that coilin knockdown and a SUMO inhibitor drug, TAK-981, influence the dynamics of PARP1 in response to micro-irradiation. Additionally, we find that the SUMOylation status of coilin influences its mobility in the CB and recruitment to sites of DNA damage. These data demonstrate that coilin and SUMOylation both have an influence on the DNA damage response.