cell cycle and cancer

cell cycle and cancer - Proc Natl Acad Sci USA Vol 94 pp...

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Proc. Natl. Acad. Sci. USA Vol. 94, pp. 2776–2778, April 1997 From the Academy This paper serves as a summary of a symposium session as part of the Frontiers of Science series, held November 7–9, 1996, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The cell cycle and cancer K ATHLEEN C OLLINS *, T YLER J ACKS ² , AND N IKOLA P. P AVLETICH *Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; ² Howard Hughes Medical Institute and Department of Biology, Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139; and Cellular Biochemistry and Biophysics Program, Memorial Sloan–Kettering Cancer Center, New York, NY 10021 Recent insights in the fields of cell cycle regulation and cancer would each alone have provided prime examples of research at the ‘‘Frontiers of Science.’’ However, some of the most revealing information about both topics has derived from the intersection of the two fields. The intent of this summary is to introduce the basics of the cell cycle, cancer, and their overlap, and then to describe the research from two laboratories that was presented in the session. A more comprehensive treatment of these subjects, beyond this description for a general audience, is contained in several reviews (1–5). The process of replicating DNA and dividing a cell can be described as a series of coordinated events that compose a ‘‘cell division cycle,’’ illustrated for mammalian cells in Fig. 1 (see legend for details). At least two types of cell cycle control mechanisms are recognized: a cascade of protein phosphory- lations that relay a cell from one stage to the next and a set of checkpoints that monitor completion of critical events and delay progression to the next stage if necessary. The first type of control involves a highly regulated kinase family (2). Kinase activation generally requires association with a second subunit that is transiently expressed at the appropriate period of the cell cycle; the periodic ‘‘cyclin’’ subunit associates with its partner ‘‘cyclin-dependent kinase’’ (CDK) to create an active complex with unique substrate specificity. Regulatory phos- phorylation and dephosphorylation fine-tune the activity of CDK–cyclin complexes, ensuring well-delineated transitions between cell cycle stages. In the future, additional molecular definition of the cell cycle may lead to a more intricate progression than indicated in Fig. 1. A second type of cell cycle regulation, checkpoint control, is more supervisory. It is not an essential part of the cycle progression machinery. Cell cycle checkpoints sense flaws in critical events such as DNA replication and chromosome segregation (4). When checkpoints are activated, for example by underreplicated or damaged DNA, signals are relayed to the cell cycle-progression machinery. These signals cause a delay in cycle progression, until the danger of mutation has been
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cell cycle and cancer - Proc Natl Acad Sci USA Vol 94 pp...

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