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Cyclins bind with and activate cyclin-dependent kinases (CDKs) to control progression through the cell cycle in eukaryotes. Active CDKs regulate cell cycle progression by phosphorylating specific substrates and initiating the transition from G1 to S phase and G2 to M phase. Cyclins A, B, D, and E are synthesized and degraded at different times within the cell cycle, which generates a predictable protein expression pattern (figure 1). The elevated cyclin levels cause specific CDKs to become active and trigger progression through the cell cycle. Conversely, the timely enzymatic degradation of cyclins causes the respective CDK to become inactive – failure to degrade cyclins can arrest the cell cycle.
You can use specific antibodies to target individual cyclins to monitor a cell’s progression through the cell cycle.
Figure 1. The changing levels of cyclin proteins throughout the cell cycle.
Cyclin A associates preferentially with CDK2, but can also pair with CDK1, and regulates the completion of S phase.
Recommended antibody: Anti-Cyclin A1 + Cyclin A2 antibody [EPR18054] (ab185619)
Figure 2. Immunohistochemical analysis of paraffin-embedded human testis tissue labeled with anti-Cyclin A1 + Cyclin A2 [EPR18054] (ab185619) at 1/2,000 dilution. The secondary antibody was goat anti-rabbit IgG H&L (HRP) (ab97051) at 1/500.
Cyclin B associates preferentially with CDK1, but can also pair with CDK2, and is essential to progress into mitosis.
Recommended antibody: Anti-Cyclin B1 antibody [Y106] (ab32053) (knockout validated)
Figure 3. Immunocytochemical analysis of U2OS cells labeled with anti-Cyclin B1 [Y106] (ab32053) (red) at 1/1,000. The secondary antibody was Alexa 594 goat anti-rabbit. Nuclei were counterstained with DAPI (blue). Cyclin B1 accumulates as cells enter G2
Cyclin D associates preferentially with CDK4 and CDK6, but can also pair with CDK1 and CDK2, and is required for G1/S transition. . Immunohistochemical analysis of cyclin D1 in also used in the diagnosis of certain cancers
Recommended antibody: Anti-Cyclin D1 antibody [EPR2241] (ab134175)
Recommended kit: Human Cyclin D1 SimpleStep ELISA® kit (ab214571)
Recommended compound: S14161 (ab144352) (inhibits cyclin D1-D3 to arrest dividing cells).
Figure 4. Immunocytochemical analysis of MCF7 cells treated with KN-93 (ab120980) and labeled with unpurified anti-Cyclin D1 [EPR2241] (ab134175) at 10μg/mL. The secondary antibody was anti-rabbit Alexa 488 secondary (ab150081) at 2 μg/mL (shown in green) and goat anti-mouse Alexa Fluor 594 (ab150120) at 2 μg/mL (shown in pseudocolor red). Nuclei were counterstained with DAPI (blue).
Cyclin E associates preferentially with CDK2, but can also pair with CDK1, and triggers the transition to S phase.
Recommended antibody: Anti-Cyclin E1 antibody [EP435E] (ab33911)
Figure 5. Immunocytochemical analysis HeLa cells labeled with anti-Cyclin E1 [EP435E] (ab33911) at 1/500. The secondary antibody was Alexa 488 goat anti-rabbit IgG used at 1/1,000. Nuclei were counterstained with DAPI (blue).