The selective post-translational processing of transcription factor Nrf1 yields distinct isoforms that dictate its ability to differentially regulate gene expression.
The selective post-translational processing of transcription factor Nrf1 yields distinct isoforms that dictate its ability to differentially regulate gene expression.
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转录因子 Nrf1 的选择性翻译后加工产生不同的亚型，决定了其差异调节基因表达的能力
DOI：
10.1038/srep12983
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发表时间：
2015-08-13
影响因子：
4.6
通讯作者：
Hayes JD
中科院分区：
文献类型：
--
作者：
Zhang Y;Li S;Xiang Y;Qiu L;Zhao H;Hayes JD
翻译后，Nrf1 的 N 端同源盒 1 (NHB1) 信号锚序列将其整合到内质网 (ER) 内，同时其反式激活结构域 [TAD，包括酸性结构域 1 (AD1)、侧翼富含 Asn/Ser/Thr (NST) 结构域和 AD2] 瞬时易位到 ER 腔中，随后 NST 结构域被糖基化，产生无活性的120-kDa 糖蛋白。随后，这些 TAD 被逆转录至腔外亚细胞区室，其中 Nrf1 被去糖基化，产生活性 95-kDa 亚型。在此，我们报告 AD1 和 AD2 对于 120-kDa Nrf1 糖蛋白的稳定性是必需的，但对于非糖基化/去糖基化的 95-kDa 亚型则不是必需的。 AD1 内的降解决定子不会促进 120-kDa Nrf1 糖蛋白的蛋白水解降解。然而，将 AD2 邻接的降解决定子（即包含 DSGLS 的 SDS1 和 PEST2 序列）重新定位到细胞/核质中，使得蛋白酶体和/或钙蛋白酶能够选择性地对 Nrf1 进行拓扑矢量加工，从而生成切割的活性 85-kDa Nrf1 或显性失活的 36-kDa Nrf1γ。通过去除 SDS1 或 PEST2 降解决定子，可以消除 Nrf1γ 的产生，而通过删除 ER 腔锚定 NHB2 序列 (aa 81-106)，可以阻止切割的 85-kDa Nrf1 的产生。重要的是，Nrf1 活性受到不同剂量的蛋白酶体和钙蛋白酶抑制剂的正向和/或负向调节。
Upon translation, the N-terminal homology box 1 (NHB1) signal anchor sequence of Nrf1 integrates it within the endoplasmic reticulum (ER) whilst its transactivation domains [TADs, including acidic domain 1 (AD1), the flanking Asn/Ser/Thr-rich (NST) domain and AD2] are transiently translocated into the ER lumen, whereupon the NST domain is glycosylated to yield an inactive 120-kDa glycoprotein. Subsequently, these TADs are retrotranslocated into extra-luminal subcellular compartments, where Nrf1 is deglycosylated to yield an active 95-kDa isoform. Herein, we report that AD1 and AD2 are required for the stability of the 120-kDa Nrf1 glycoprotein, but not that of the non-glycosylated/de-glycosylated 95-kDa isoform. Degrons within AD1 do not promote proteolytic degradation of the 120-kDa Nrf1 glycoprotein. However, repositioning of AD2-adjoining degrons (i.e. DSGLS-containing SDS1 and PEST2 sequences) into the cyto/nucleoplasm enables selective topovectorial processing of Nrf1 by the proteasome and/or calpains to generate a cleaved active 85-kDa Nrf1 or a dominant-negative 36-kDa Nrf1γ. Production of Nrf1γ is abolished by removal of SDS1 or PEST2 degrons, whereas production of the cleaved 85-kDa Nrf1 is blocked by deletion of the ER luminal-anchoring NHB2 sequence (aa 81–106). Importantly, Nrf1 activity is positively and/or negatively regulated by distinct doses of proteasome and calpain inhibitors.