Figure 1. Ybp2 has a mitotic function.

(A) The ybp2Δ mutant is sensitive to benomyl. Wild-type (BY4741), ybp2Δ (Y1028), and mad2Δ (Y516) strains were spotted in 5-fold dilutions from 5×10⁴ cells per spot on YPD plates containing 20 µg/mL benomyl and incubated at 25°C for 3 days. (B) The ybp2Δ cells accumulate at G2/M. Logarithmically growing cells, wild type (Y14) and ybp2Δ (Y1831), were cultured at 25°C and processed for flow cytometry. (C) Double mutants of ybp2Δ and the spindle checkpoint genes show temperature-dependent synthetic lethality. Yeast strains were spotted in 5-fold dilutions from 5×10⁴ cells per spot on YPD plates. The plates were incubated at the indicated temperatures for 2 days. Isogenic yeast strains were wild type (YPH500), ybp2Δ (Y1342), mad1Δ (Y550), mad2Δ (Y1323), mad3Δ (Y554), bub1Δ (Y530), bub3Δ (Y548), ybp2Δmad1Δ (Y1398), ybp2Δmad2Δ (Y1419), ybp2Δmad3Δ (Y1402), ybp2Δbub1Δ (Y1415), and ybp2Δbub3Δ (Y1396). (D) Immunofluorescence analysis of ybp2Δ cells. Logarithmically growing cells cultured at 25°C were fixed and stained with antitubulin antibodies and DAPI. The strains shown are wild type (Y14) and ybp2Δ (Y1831). For each sample, 300 cells were counted.