Figure 6
From: Yeast karyopherin Kap95 is required for cell cycle progression at Start
Coordinated spatial regulation of Start transcriptional machinery. Expression of genes at the G1/S transition is regulated by the transcription factors SBF (Swi4-Swi6), MBF (Mbp1-Swi6) and the transcriptional repressor Whi5. The four proteins Swi4, Swi6, Mbp1 and Whi5 are imported into the nucleus by the same pathway involving karyopherin Kap95 and classical NLS sequences. Swi4 and Mbp1 remains nuclear along the cell cycle. However, after Start activation Whi5 and Swi6 are exported to the cytoplasm by karyopherin Msn5, a transport that depends on the phosphorylation of the proteins. At the end of mitosis, the Cdc14 phosphatase dephoshorylates Whi5 and Swi6 to once again lead to the nuclear acumulation of the proteins.