Abstract
Ku was first identified as an autoantigen in the sera of patients with autoimmune diseases, as a heterodimer composed of subunits Ku70 and Ku80 that binds to the DNA ends, nicks, or single-to-double-strand transition. Ku plays a crucial role for DNA double-strand-break repair. Homologous of Ku70 and Ku80 in Arabidopsis were identified in 2002, with conserved sizes sharing 28.6 and 22.5% sequence identity with the respective human proteins. Further studies indicated that AtKu plays a similar role in the repair of DNA double-strand breaks by non-homologous end joining (NHEJ) pathway in response to DNA damaging agents in plants as in other organisms. Loss of AtKu results in deregulation of telomere length control. The previous studies on AtKu promoter activity under treatment of plant hormones and stress indicated that AtKu is regulated by various endogenous and exogenous factors. Some of these signals activate and others inhibit the expression of AtKu. Up to now, the mechanism of the regulation of AtKu in plants still is limited to know. In this study, we prompted to investigate the molecular mechanism of these processes by yeast one-hybrid screening. A cDNA encoding ATAF1 protein was identified. ATAF1 was reported to be induced by dehydration and ABA, as a transcriptional regulator, to negatively regulate the expression of the other stress responsive genes. To combine results on hormones and stress stimulation with that on the repressor activity of ATAF1 on transcriptional regulation, we speculate that ATAF1 may function as a transcriptional repressor to down regulate the expression of the AtKu genes.