Characterization of the Functional Roles of the E3 Ligase HUWE1 in the Regulation of Poly [ADP-ribose] Polymerase 1 (PARP-1) under DNA Damage

The Poly (ADP-ribose) polymerase 1 (PARP-1) is responsible for synthesis of polymeric ADP-ribose chain on substrate proteins associated with DNA damage repair. PARP-1 overexpression has been associated with rapid proliferation and metastasis in cancers. Ubiquitylation is a protein post-translational modification and the key bioprocess for the regulation of PARP-1 functionally. Recently, ubiquitin E3 ligase HUWE1 (HECT, UBA and WWE domain containing 1) was reported to be involved in DNA damage response. HUWE1 also possesses a functional WWE domain, which is a structural motif to recognize the ADP-ribose unit of PAR polymers. In this study, the functional roles of HUWE1 in the regulation of PARP-1 were characterized. This study reveals (1) HUWE1 could bind to cellular PAR polymers through its WWE domain. (2) As PARP-1 is modified through auto-PARylation in the cell, HUWE1 could interact with the PARylated PARP-1 via WWE domain. (3) HUWE1 could regulate PARP1 stability through ubiquitination. This study provides mechanistic insight on the regulation and the function of these two proteins in both biological and pathological conditions.