Figure 7. Model of the MAS in WT, ima1Δ and nuf2-1 cells.

A. In WT cells, the Sad1 (red) / Kms2 (green) bridging complex links the MTOC (SPB, orange) to the centromeric heterochromatin (lavender/gray). Ima1 (purple) resides at the inner nuclear membrane and contributes to the coupling of heterochromatin to the inner MAS. The Ndc80 complex (yellow) also participates in linking the centromeres to the inner MAS, through an unknown adapter (blue) and Sad1. B. Without Ima1, the Ndc80 complex (yellow) is not sufficient to tightly couple centromeres to the MAS, leading to large nuclear envelope (NE) deformations. C. In the absence of Ima1, fragmentation of the MAS occurs and Sad1-Kms2 lumenal interactions are disrupted, decoupling forces delivered on the NE by the SPB from the centromeres and other MAS components. D. In nuf2-1 cells, Ima1 is not sufficient to couple centromeres to the MAS, resulting in large NE deformations.