Figure 5.

TET1/2 Stabilize Cyclin B1

(A) Western blots to determine cyclin B1 (CCNB1) and cyclin D1 (CCND1) stability in TSCs treated with the translation inhibitor emetine for the indicated time periods.

(B) Quantification of band intensities (n = 4 independent replicates for cyclin B1 [CCNB1]; n = 2 independent replicates for cyclin D1 [CCND1]; ^∗p < 0.05 [two-way ANOVA with Holm-Sidak's multiple comparisons test]. 0 hr value was set to 1.

(C) Analysis of cyclin B1 (CCNB1) levels following combined translation and proteasome inhibition with emetine (Em) and MG132 over the indicated time points.

(D) Western blot of TET1 co-immunoprecipitates from ESCs assessed for cyclin B1 (CCNB1) interaction.

(E) Model of cell-cycle defects induced by loss of TET1/2 depletion in TSCs. TET1/2 depletion results in CDKN1A (P21) upregulation, as well as enhanced cyclin B1 (CCNB1) degradation, both rendering CDK1 inactive. CDK1 inactivation prevents phosphorylation of CDK1 substrates, such as ATF7, which promotes M-phase entry via stabilization of AURKB, and the motor protein EG5, which is involved in bipolar spindle formation. Collectively, a defective G2/M progression results in bypass of mitosis and entry into the endocycle.

See also Figure S5.