Fig. 3. NuMA tail IIA co-localizes with microtubules in interphase cells and induces the formation of straight and stable microtubule bundles. (A) Cells expressing GFP-NuMA tail fragments (tail I, tail II or tail IIA), fixed and processed for immunofluorescence of tubulin (left column), corresponding fluorescence of the GFP-tag (middle column), and merged fluorescence (right column). Red, tubulin; green, GFP; blue, chromosomes stained with DAPI. Bar, 20 µm. (B) Cell expressing GFP-NuMA tail IIA, fixed and processed for fluorescence microscopy of GFP (upper left panel), followed by electron microscopy. Lower left panel: low magnification electron micrograph of the same cell, upper and lower right panels: high magnification views showing microtubule bundles in areas 1 and 2, as indicated by arrows in the GFP fluorescence micrograph. Bar, 1 µm. (C,D) Cells expressing GFP-NuMA tail IIA (green), fixed and processed for immunofluorescence of endogenous NuMA (C, red), or fluorescence of actin using rhodamine-phalloidin (D, red). Bars, 20 µm (C,D). (E) Diagram of the various human NuMA constructs used for transfection experiments. Amino acid positions are indicated.