ABSTRACT
Redox factor-1 (Ref-1) is a bifunctional protein playing an important role in both cellular redox regulation and DNA apurinic/apyrimidinic sites' repair. To find Ref-1interacting proteins (Rips), a yeast two-hybrid screening was performed by using Ref-1 redox domain as the 'bait', and five positive clones were obtained. One of them (Rip3) was identified to be the ubiquitin-conjugating enzyme Ubc9. Simultaneous overexpression of Ubc9 in Hela cells dramatically inhibited the enhancement of AP-1 reporter gene by Ref-1. Western blot indicated that the protein level of Ref-1 dropped down as the result of simultaneous overexpression of Ubc9. These results suggest that Ubc9 is involved in the protein degradation of Ref-1, resulting in the downregulation of Ref-1 physiological function.
