Fig. 4
From: The Id-protein family in developmental and cancer-associated pathways
Phosphorylation of Id2 and Id3. These proteins are phosphorylated by Cdk2 at the G1-S transition [46–48, 121–123] (a). Phosphorylated Id2 (or its S5D mimic) accumulates in the nucleus, whereas phosphoablated Id2 (S5A) accumulates in the cytoplasm and induces cell-cycle arrest or apoptosis [121, 122] (b). Phosphorylated Id3 induces cell-cycle progression of VSMCs via inhibiting the cell-cycle blocker p21Cip1 at the transcriptional level [123] (c). Phosphorylated Id2 is less resistant to degradation than unphosphorylated Id2. In glioblastoma high Id2 levels can be maintained by PP2A activity (d) [124]