Ubiquitin Conjugating
Enzyme Ubc9 is Involved in Protein Degradation of Redox Factor-1 (Ref-1)
YAN Ming-Da, XU Wei-Jin, LU Lin-Rong, SUN Lan-Ying, LIU
Xin-Yuan, ZHENG Zhong-Cheng*
( Shanghai Institute of Biochemistry, the Chinese Academy of Sciences,
Shanghai 200031, China )
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.
Key Words Ref-1； Ubc9； ubiquitin-mediated
protein degradation；
yeast two-hybrid system
Received: August 19,
1999 Accepted: September 27, 1999
* Corresponding author: Tel, 86-21-64374430-328; Fax, 86-21-64746127; e-mail, [email protected]