Rothenberger Sylvia, Burns Kimberly, Rousseaux Marga, Tschopp Jürg, Bron Claude
Institute of Biochemistry, University of Lausanne, ch. des Boveresses 155, 1066 Epalinges, Switzerland.
Oncogene. 2003 Aug 28;22(36):5614-8. doi: 10.1038/sj.onc.1206497.
The latent membrane protein 1 (LMP1) encoded by the Epstein-Barr virus functions as a constitutively activated receptor of the tumor necrosis factor receptor family. LMP1 is a short-lived protein that is ubiquitinated and degraded by the proteasome. We have previously shown that LMP1 recruits the adapter protein tumor necrosis factor receptor-associated factor 3 (TRAF3) to lipid rafts. To test if TRAFs are involved in LMP1's ubiquitination, we have mutated the LMP1 CTAR1 site that has been identified as a TRAF binding site. We show that the CTAR1 mutant (CTAR1(-)) is expressed after transfection at a similar level to wild-type LMP1, and behaves as wild-type LMP1 with respect to membrane localization. However, CTAR1(-) does not bind TRAF3. We demonstrate that ubiquitination of CTAR1(-) is significantly reduced when compared to wild-type LMP1. In addition, the expression of wild-type LMP1 induces the ubiquitination, an effect that is significantly reduced when the CTAR1(-) is expressed. Taken together, our results suggest that TRAF proteins are involved in the ubiquitination of LMP1, and that their binding to LMP1 may facilitate their own ubiquitination.
由爱泼斯坦-巴尔病毒编码的潜伏膜蛋白1（LMP1）作为肿瘤坏死因子受体家族的组成型激活受体发挥作用。LMP1是一种短寿命蛋白，会被蛋白酶体泛素化并降解。我们之前已表明，LMP1会将衔接蛋白肿瘤坏死因子受体相关因子3（TRAF3）招募到脂筏中。为了测试TRAFs是否参与LMP1的泛素化，我们对已被确定为TRAF结合位点的LMP1 CTAR1位点进行了突变。我们发现，CTAR1突变体（CTAR1(-)）在转染后表达水平与野生型LMP1相似，并且在膜定位方面表现与野生型LMP1相同。然而，CTAR1(-)不结合TRAF3。我们证明，与野生型LMP1相比，CTAR1(-)的泛素化显著减少。此外，野生型LMP1的表达会诱导泛素化，而当表达CTAR1(-)时这种效应会显著降低。综上所述，我们的结果表明TRAF蛋白参与LMP1的泛素化，并且它们与LMP1的结合可能促进自身的泛素化。
