REV7 has a dynamic adaptor region to accommodate small GTPase RAN/Shigella IpaB ligands and its activity is regulated by RanGTP/GDP switch.
Publication Type:Journal Article
Source:J Biol Chem (2019)
<p>REV7, also termed mitotic arrest-deficient 2-like 2 (MAD2L2 or MAD2B), acts as an interaction module in a broad array of cellular pathways, including translesion DNA synthesis, cell-cycle control, and nonhomologous end joining. Numerous REV7-binding partners have been identified, including the human small GTPase RAN, which acts as a potential upstream regulator of REV7. Notably, the Shigella invasin IpaB hijacks REV7 to disrupt cell-cycle control in order to prevent intestinal epithelial cell renewal and facilitate bacterial colonization. However, the structural details in the REV7-RAN and REV7-IpaB interactions are mostly unknown. Here, using fusion protein and rigid maltose-binding protein (MBP)-tagging strategies, we determined the crystal structures of these two complexes at 2.00-2.35 Å resolutions. The structures revealed that both RAN and IpaB fragments bind the "safety-belt" region of REV7, inducing the rearrangement of the C-terminal β-sheet region of REV7 conserved among REV7-related complexes. Of note, the REV7-binding motifs of RAN and IpaB each displayed some unique interactions with REV7 despite sharing consensus residues. Structural alignments revealed that REV7 has an adaptor region within the safety-belt region that can rearrange secondary structures to fit a variety of different ligands. Our structural and biochemical results further indicated that REV7 preferentially binds GTP-bound RAN, implying that a GTP/GDP-bound transition of RAN may serve as the molecular switch that controls REV7's activity. These results provide insights into the regulatory mechanism of REV7 in cell-cycle control, which may help aid in the development of small-molecule inhibitors that target REV7 activity.</p>