Comment on

• p21 is a universal inhibitor of cyclin kinases.

  Xiong Y, Hannon GJ, Zhang H, Casso D, Kobayashi R, Beach D. Xiong Y, et al. Nature. 1993 Dec 16;366(6456):701-4. doi: 10.1038/366701a0. Nature. 1993. PMID: 8259214
• A new regulatory motif in cell-cycle control causing specific inhibition of cyclin D/CDK4.

  Serrano M, Hannon GJ, Beach D. Serrano M, et al. Nature. 1993 Dec 16;366(6456):704-7. doi: 10.1038/366704a0. Nature. 1993. PMID: 8259215
• Inhibition of CDK2 activity in vivo by an associated 20K regulatory subunit.

  Gu Y, Turck CW, Morgan DO. Gu Y, et al. Nature. 1993 Dec 16;366(6456):707-10. doi: 10.1038/366707a0. Nature. 1993. PMID: 8259216