Figure 4.

Degradation of Grr1p and Cdc4p requires components of the SCF. (A) Degradation of Grr1p-myc is independent of an intact APC. The half-life of Grr1p-myc was determined as above in cdc16–1 cells defective for APC function (JMG62; Lower) or wild-type cells (JMG101; Upper). (B) Degradation of Grr1p-myc and Cdc4p-myc requires an intact SCF. The half-life of Grr1p-myc (upper three panels) or Cdc4p-myc (bottom panel) was determined in cells defective for the indicated SCF components. (C) The stability of Grr1p-myc (upper two panels) and Cdc4p-myc (lower three panels) was analyzed in cells harboring different alleles of SKP1: skp1–11 cells are defective for SCF^Cdc4 function, whereas skp1–12 cells become arrested in G₂ and are defective for SCF^Grr1 function (12). Note that Grr1p-myc is efficiently degraded in skp1–11 cells (JMG31), but stable in skp1–12 cells (JMG29). Conversely, Cdc4p-myc is stable in skp1–11 cells (JMG70) but partially degraded in skp1–12 cells (JMG69).