Tts1, the fission yeast homologue of the TMEM33 family, functions in NE remodeling during mitosis.
Bottom Line: An amphipathic helix located at the C-terminus of Tts1 is important for ER shaping and modulating the mitotic NPC distribution.Of interest, the evolutionarily conserved residues at the luminal interface of the third transmembrane region function specifically in promoting SPB-NE insertion.Our data illuminate cellular requirements for remodeling the NE during "closed" nuclear division and provide insight into the structure and functions of the eukaryotic TMEM33 family.
Affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 email@example.com firstname.lastname@example.org.Show MeSH
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Mentions: To determine domains important for Tts1 function in the context of mitotic SPB-NE interaction and spindle assembly, we performed complementation analyses by introducing the tts1 mutants described earlier (Figure 1) into the cut11-6 tts1Δ genetic background. All mutants that failed to partition to the ER tubules did not rescue spindle defects in cut11-6 tts1Δ cells (Figure 7A), suggesting that the structural traits specifying localization of Tts1 to the curved ER membranes may be pertinent to its function in SPB-NE insertion. However, the mutant Tts1 proteins where the C-terminal amphipathic helix was disrupted fully rescued the spindle defects in cut11-6 tts1Δ cells in spite of their compromised tubular ER-shaping function (Figure 7A). Moreover, point mutations (P119A, Y123/131I, and H127A) in the conserved residues within the third membrane-spanning region of Tts1 that did not lead to obvious ER architecture defects (Figures 1 and 2, Supplemental Figure S2F, and unpublished data) rendered Tts1 nonfunctional with respect to mitotic spindle assembly (Figure 7A). These observations suggested that the role of Tts1 in promoting SPB insertion was distinct from its functions in sustaining the ER morphology.
Affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 email@example.com firstname.lastname@example.org.