Cell Cycle Phase Determination Antibody Sampler Kit

The Cell Cycle Phase Determination Antibody Sampler Kit provides an economical means of detecting total proteins or post-translational modifications present in cells at various phases of the cell cycle. Geminin is degraded in G1 phase, while CDT1 is degraded in S, G2, and M phases. Thymidine Kinase 1 accumulates in G1 phase, peaks in S phase, and is degraded before cell division. Phospho-Histone H3 (Ser10) is present only in M phase, while Phospho-cdc2 (Tyr15) is absent in M phase. Cyclins A2, B1, and E1 peak at G2 phase, late G2/M phase, and late G1/early S phase, respectively. The kit includes enough antibodies to perform two western blot experiments with each primary antibody.

The entry of eukaryotic cells into mitosis is regulated by cdc2/CDK1 kinase activation, a process controlled at several steps including cyclin B1 nuclear accumulation and binding, and phosphorylation of cdc2/CDK1 at Thr161 (1). At the end of mitosis, cyclin B1 is targeted for degradation by the anaphase-promoting complex (APC), allowing for cell cycle progression (2). A critical regulatory step in activating cdc2 during progression into mitosis is dephosphorylation of cdc2/CDK1 at Thr14 and Tyr15 (3).
Phosphorylation of Histone H3 at Ser10 is tightly correlated with chromosome condensation during both mitosis and meiosis (4).
Overcoming the G1/S checkpoint to commence DNA replication requires cyclin E, traversing the G2/M checkpoint to initiate mitosis requires cyclin B, and cyclin A is required for both S-phase and M-phase (5). Cyclin A availability is apparently the rate-limiting step for entry into mitosis, and cyclin A is required for completion of prophase (6).
Thymidine kinases play a critical role in generating the DNA synthetic precursor deoxythymidine triphosphate (dTTP). Cytoplasmic thymidine kinase 1 (TK1) expression and activity are regulated in a cell cycle-dependent manner, accumulating during G1-phase to peak levels in S-phase before being degraded prior to cell division (7).
The initiation of S phase begins with the formation of the pre-replication complex (pre-RC) in late mitosis/early G1 phase. CDT1 and cdc6 bind to the origin of DNA replication, which allows binding of the MCM2-7 complex. In order to ensure that replication occurs only once per cell cycle, geminin inhibits and destabilizes CDT1 during the S, G2 and M phases. At the metaphase/anaphase transition, geminin is degraded by the anaphase-promoting complex (APC) allowing for the formation of new pre-RC (8).