• BMB Reports
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• v.41 no.8
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• pp.575-580
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• 2008

Thymocyte-specific transcriptional regulatory systems can be used to better understand the relationship between transcription and V(D)J recombination during early T cell development. In this study, we generated transgenic mice expressing the transactivator Gal4-VP16 or the Gal4 DNA binding domain (Gal4-DBD) under the control of the lck proximal promoter, which is only active in immature thymocytes. From these studies Gal4-VP16 and Gal4-DBD expression was shown to significantly alter thymic cellularity and differentiation without significantly changing the $CD3^+$ thymocyte distribution. Furthermore, the presence of Gal4-VP16 or Gal4-DBD in the transgenic thymocytes retarded the mobility of the Gal4 DNA binding motif as determined by a gel mobility shift assay, suggesting that the developmental alteration did not affect the functional property of the transgenic proteins. These results indicated that lck promoter-driven Gal4-VP16 or Gal4-DBD expression did not affect $CD3^+$ mature thymocytes, thus this system can be applied to study transcriptional regulation of transresponder genes in bigenic mouse model thymocytes.

• Molecules and Cells
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• v.42 no.11
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• pp.783-793
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• 2019

When endoplasmic reticulum (ER) functions are perturbed, the ER induces several signaling pathways called unfolded protein response to reestablish ER homeostasis through three ER transmembrane proteins: inositol-requiring enzyme 1 (IRE1), PKR-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Although it is important to measure the activity of ATF6 that can indicate the status of the ER, no specific cell-based reporter assay is currently available. Here, we report a new cell-based method for monitoring ER stress based on the cleavage of $ATF6{\alpha}$ by sequential actions of proteases at the Golgi apparatus during ER stress. A new expressing vector was constructed by using fusion gene of GAL4 DNA binding domain (GAL4DBD) and activation domain derived from herpes simplex virus VP16 protein (VP16AD) followed by a human $ATF6{\alpha}$ N-terminal deletion variant. During ER stress, the GAL4DBD-VP16AD(GV)-$hATF6{\alpha}$ deletion variant was cleaved to liberate active transcription activator encompassing GV-$hATF6{\alpha}$ fragment which could translocate into the nucleus. The translocated GV-$hATF6{\alpha}$ fragment strongly induced the expression of firefly luciferase in HeLa Luciferase Reporter cell line containing a stably integrated 5X GAL4 site-luciferase gene. The established double stable reporter cell line HLR-GV-$hATF6{\alpha}$(333) represents an innovative tool to investigate regulated intramembrane proteolysis of $ATF6{\alpha}$. It can substitute active pATF6(N) binding motif-based reporter cell lines.

• BMB Reports
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• v.32 no.3
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• pp.279-287
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• 1999

The aromatic hydrocarbon receptor (AhR) is a cytosolic protein that binds the environmental pollutant, dioxin. The liganded AhR translocates into the nucleus where it heterimerizes with a constitutive nuclear protein, AhR nuclear translocator (Arnt). The N-terminal regions of both AhR and Arnt contain basic helix-loop-helix (bHLH) and Per-AhR-Arnt-Sim (PAS) motifs that are required for DNA binding, dimerization, and ligand binding whereas the C-terminal regions of both AhR and Arnt contain transactivation domains. Here, results from the mammalian two-hybrid system indicate that Arnt can make a homodimer but AhR cannot. In the presence of dioxin, the interaction between AhR and Arnt is stronger than that of the Arnt homodimer, suggesting that Arnt prefers to make a heterodimer with the liganded AhR rather than a homodimer. Transfection analyses using the GAL4-driven reporter system suggest that AhR's N-terminal region represses its own transactivation domain, as well as exogenous transactivation domains such as Sp 1 and VP16. Interestingly, the repressed transactivation domains of AhR are activated by ligand-dependent heterodimerization with Arnt. These observations suggest that heterodimerzation with Arnt is necessary not only for DNA binding but also for activation of the repressed transactivation capability of AhR.