Wang Xiao-Gan, Wang Zhao-Qi, Tong Wei-Min, Shen Yan
National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences (CAMS) and Peking Union Medical College (PUMC), 5 Dong Dan San Tiao, 100005 Beijing, PR China.
Biochem Biophys Res Commun. 2007 Mar 2;354(1):122-6. doi: 10.1016/j.bbrc.2006.12.162. Epub 2006 Dec 29.
Poly(ADP-ribose) polymerase 1 (PARP1) modifies a variety of nuclear proteins by poly(ADP-ribosyl)ation, and plays diverse roles in molecular and cellular processes. A common PARP1 single nucleotide polymorphism (SNP) at codon 762, resulting in the substitution of alanine (Ala) for valine (Val) in the catalytic domain has been implicated in susceptibility to cancer. To characterize the functional effect of this polymorphism on PARP1, we performed in vitro enzymatic analysis on PARP1-Ala762 and PARP1-Val762. We found that PARP1-Ala762 displayed 57.2% of the activity of PARP1-Val762 for auto-poly(ADP-ribosyl)ation and 61.9% of the activity of PARP1-Val762 for trans-poly(ADP-ribosyl)ation of histone H1. The kinetic characterization revealed that the K(m) of PARP1-Ala762 was increased to a 1.2-fold of the K(m) of PARP1-Val762 for trans-poly(ADP-ribosyl)ation. Thus, the PARP1 Val762Ala polymorphism reduces the enzymatic activity of PARP1 by increasing K(m). This finding suggests that different levels of poly(ADP-ribosyl)ation by PARP1 might aid in understanding the cancer risk of carriers of the PARP1 Val762Ala polymorphism.
聚（ADP-核糖）聚合酶1（PARP1）通过聚（ADP-核糖基）化修饰多种核蛋白，并在分子和细胞过程中发挥多种作用。位于密码子762的常见PARP1单核苷酸多态性（SNP）导致催化结构域中的丙氨酸（Ala）被缬氨酸（Val）取代，这与癌症易感性有关。为了表征这种多态性对PARP1的功能影响，我们对PARP1-Ala762和PARP1-Val762进行了体外酶活性分析。我们发现，PARP1-Ala762的自聚（ADP-核糖基）化活性为PARP1-Val762的57.2%，对组蛋白H1的转聚（ADP-核糖基）化活性为PARP1-Val762的61.9%。动力学表征显示，PARP1-Ala762的K(m)增加至PARP1-Val762转聚（ADP-核糖基）化K(m)的1.2倍。因此，PARP1 Val762Ala多态性通过增加K(m)降低了PARP1的酶活性。这一发现表明，PARP1不同水平的聚（ADP-核糖基）化可能有助于理解PARP1 Val762Ala多态性携带者的癌症风险。
