Structural and functional characterization of tumor suppressors TIG3 and H-REV107

Area of Science:

• Molecular biology
• Cell biology
• Cancer research

Background:

• H-REV107-like family proteins, including TIG3 and H-REV107, function as class II tumor suppressors.
• Understanding the specific roles of protein domains is crucial for elucidating tumor suppressor mechanisms.

Purpose of the Study:

• To investigate the cell death-inducing capabilities of the C-terminal domains (CTDs) of TIG3 and H-REV107.
• To determine the modulatory roles of the N-terminal domains (NTDs) of TIG3 and H-REV107 on their respective CTDs.
• To explore the structural basis for the functional differences between TIG3 and H-REV107 NTDs.

Main Methods:

• Cell death assays using HeLa cells to assess the function of TIG3 and H-REV107 domains.
• Solution structure determination of TIG3 NTD.
• Comparative structural analysis of TIG3 and H-REV107 NTDs.
• Functional analysis of specific structural regions, such as the main loop of H-REV107 NTD.

Main Results:

• Both TIG3 CTD and H-REV107 CTD can independently induce HeLa cell death.
• TIG3 NTD enhances the cell death-inducing activity of its CTD, whereas H-REV107 NTD inhibits its CTD's activity.
• While TIG3 and H-REV107 NTDs share similar overall folds, their CTD binding regions differ.
• A flexible main loop in H-REV107 NTD is critical for modulating its CTD's cell death induction, a role not observed for TIG3.

Conclusions:

• The differential modulation of CTD activity by the NTDs of TIG3 and H-REV107 contributes to their distinct roles as tumor suppressors.
• Structural differences in NTD-CTD interaction regions, particularly the H-REV107 main loop, underlie their opposing regulatory functions.
• These findings provide insights into the complex mechanisms of H-REV107-like tumor suppressors and potential therapeutic targets.