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: The NPCs marked by Cut11-GFP remained evenly distributed around the NE throughout mitosis in wild-type S. pombe, as the mother nucleus divided into two daughters through a dumbbell-shaped intermediate (Figure 3A, top; the nuclear membrane was labeled by Uch2-mCherry, and Pcp1-mCherry traced the SPBs). Of interest, in 46% of mitotic tts1Δ cells, Cut11-GFP clustered in large aggregates at the NE (34 of 74 cells; Figure 3A, bottom) at the stage when the nuclear membrane expanded dramatically to allow formation of the two daughter nuclei (Lim et al., 2007; Yam et al., 2011). These clusters of Cut11-marked NPCs protruded outward during nuclear division (Figure 3A, bottom). The nuclear membrane marker Uch2-mCherry was also present in the protrusions, arguing that these structures represented deformations of the entire NE (Figure 3A, bottom membrane protrusions indicated by arrows). In line with this, we observed similar deformations of the dividing NE using the nuclear basket protein Nup211-GFP, the fission yeast homologue of Mlp1/Tpr known to associate with the inner nuclear side of the NPCs (Strambio-de-Castillia et al., 1999; Bae et al., 2009; 10 of 14 cells; Figure 3B). These NPC-enriched NE extensions did not incorporate into the daughter nuclei (Figure 3, A and B). Yet Cut11 levels at mitotic SPBs or total cellular levels of Cut11 remained unaltered in cells lacking Tts1 (Supplemental Figure S2, C and D). We did not observe abnormal NPC clustering or overt NE shape abnormalities in interphase tts1Δ cells (unpublished data).
Affiliation: Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604 email@example.com firstname.lastname@example.org.