Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata 700 064, India.
Nucleic Acids Res. 2010 Jan;38(3):878-92. doi: 10.1093/nar/gkp1011. Epub 2009 Nov 24.
Earlier we have shown that exogenous expression of HIPPI, a molecular partner of Huntingtin interacting protein HIP-1, induces apoptosis and increases expression of caspases-1, -8 and -10 in HeLa and Neuro2A cells. The C-terminal pseudo death effector domain of HIPPI (pDED-HIPPI) specifically interacts with the putative promoter sequences of these genes. In the present manuscript, we predict from structural modeling of pDED-HIPPI that R393 of HIPPI is important for such interaction. R393E mutation in pDED-HIPPI decreases the interaction with the putative promoter of caspase-1 in cells. Expression of caspase-1 is decreased in cells expressing mutant pDED-HIPPI in comparison to that observed in cells expressing wild type pDED-HIPPI. Using HIP-1 knocked down cells as well as over expressing HIP-1 with mutation at its nuclear localization signal and other deletion mutations, we demonstrate that translocation of HIPPI to the nucleus is mediated by HIP-1 for the increased expression of caspase-1. HIPPI-HIP-1 heterodimer is detected in cytoplasm as well as in the nucleus and is associated with transcription complex in cells. Taking together, we are able to show the importance of R393 of HIPPI and the role of HIPPI-HIP-1 heterodimer in the transcription regulation of caspase-1.
先前我们已经证明，Huntingtin 相互作用蛋白 HIP-1 的分子伴侣 HIPPI 的外源表达会诱导细胞凋亡，并增加 HeLa 和 Neuro2A 细胞中 caspase-1、-8 和 -10 的表达。HIPPI 的 C 末端假死亡效应结构域（pDED-HIPPI）特异性地与这些基因的假定启动子序列相互作用。在本手稿中，我们根据 pDED-HIPPI 的结构建模预测，HIPPI 的 R393 对这种相互作用很重要。pDED-HIPPI 中的 R393E 突变会降低与细胞中 caspase-1 假定启动子的相互作用。与表达野生型 pDED-HIPPI 的细胞相比，表达突变型 pDED-HIPPI 的细胞中 caspase-1 的表达减少。通过敲低 HIP-1 的细胞以及过表达具有核定位信号突变和其他缺失突变的 HIP-1，我们证明了 HIPPI 向核内的易位是由 HIP-1 介导的，从而导致 caspase-1 的表达增加。在细胞质和细胞核中都检测到 HIPPI-HIP-1 异二聚体，并与细胞中的转录复合物相关联。总之，我们能够证明 HIPPI 的 R393 的重要性以及 HIPPI-HIP-1 异二聚体在 caspase-1 转录调控中的作用。
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