Figure 4.

Poc1 exhibits both dynamic and stable incorporation at basal bodies. (A) GFP-Poc1 protein incorporation during basal body assembly. Noninduced cells exhibited no fluorescence signal. GFP-Poc1 expressed for 2 h in cells arrested for 12 h to inhibit basal body assembly. Low fluorescence uniformly incorporated at all basal bodies. Cells were released from the arrest for 2 h in the presence of GFP-Poc1. Dim GFP-Poc1 signal was found at existing, mature basal bodies (arrowhead), whereas newly assembled basal bodies contained bright GFP-Poc1 (arrow). Uniform anticentrin staining was observed at all basal bodies. 8 h after release, the majority of the basal bodies were brightly labeled. In contrast to the 2-h release, at 8 h, new basal bodies in dividing cells were dim (arrow) compared with old basal bodies (arrowhead). (B) FRAP to quantify the dynamic fraction of GFP-Poc1 in poc1Δ cells. After photobleaching, fluorescence recovery was followed. (bottom) Open diamonds indicate the mean fluorescence recovery relative to the best-fit single exponential recovery (filled squares). Arrowheads indicate the photobleached basal body. (C) GFP-Poc1 decorates all basal bodies uniformly upon expression in cycling cells for 2 h in a poc1Δ strain. Bars, 1 µm.