Figure 6.

Anillin, actin, and RBK6 localize to the equatorial cell cortex in the absence of a central spindle. (A) RB6K is normally found throughout the equatorial midzone during late anaphase in control cells (a and c). In cells lacking PRC1 (b and d), RB6K is fully dispersed at the beginning of anaphase, but associates with the equatorial cortex when furrowing initiates. Cells were labeled for RB6K (green), α-tubulin (red), and DNA (blue). (B) Normal anillin association with the cortex in late anaphase and telophase, as shown in control cell (a and c), is not affected by the lack of PRC1 (b and d), here identified by the absence of a central spindle bundle. Anaphase cells (a and b) were stained for anillin (blue), α-tubulin (red), and Aurora B (green). Telophase cells (c and d) were stained for anillin (green), α-tubulin (red), and DNA (blue). Bar, 5 μm. (C) Actin cortical distribution found in untreated cells in late anaphase (a) and telophase (c) is not altered by the absence of a central spindle bundle in PRC1 ablated cells (b, anaphase; d, telophase). HeLa cells were stained for actin (blue), α-tubulin (red), and PRC1 (green). (D) RB6K associates with the equatorial cortex in the absence of PRC1. In a control cell (a) RB6K colocalizes with Aurora B and with astral microtubule plus ends at the cortex, and at the central spindle bundle. In siRNA-treated cells (b–d) RB6K is present at the equatorial cortex with Aurora B, although it apparently associates with astral microtubule plus ends more internally, both in early anaphase (b) and in late anaphase/telophase (c and d). Bar, 5 μm.