FIG. 4.

Dbf4p is present in the nuclei of late G₁- to metaphase-arrested cells. Wild-type and cdc mutant cells expressing an integrated ProA-tagged copy of Dbf4p were arrested in different stages of the cell cycle either by using chemicals or by growth of the cdc mutant at the restrictive temperature. Immunofluorescence was performed on these cells as described in Materials and Methods. Two views of each field are shown, Dbf4-ProA staining (fluorescein isothiocyanate [FITC]) and staining of DNA (DAPI). All photographs were taken with a 100× objective and printed at the same magnification. cdc4-1 mutants form abnormal buds (44). The same cultures were used for immunoblot analysis (Fig. 2). HU, hydroxyurea; NZ, nocodazole.