Fig. 4. Wsp1 localization to sites of cell growth requires Nak1. (A) WSP3-12B (wsp1) cells expressing Wsp1-GFP from an adh1 promoter expression plasmid were grown to mid-log phase in minimal medium and stained with TRITC-phalloidin (top) or calcofluor (bottom), and examined by fluorescence microscopy. (B) TYH1 (nmt1-nak1) cells expressing Wsp1-GFP were grown in the absence (+Nak1) or presence (–Nak1) of 100 µg ml^–1 thiamine for 18 hours to repress endogenous nak1 expression. TYH1 (nmt1-nak1) cells coexpressing Wsp1-GFP and Nak1^T171A (+Nak1^T171A) were also examined following endogenous nak1 repression.