Cell-cycle control system

It is uncertain whether the intrinsic timer in OPCs primarily controls the onset of differentiation, the cessation of proliferation, or both. It seems likely, however, that the timer at some point interacts with the cell-cycle control system that regulates progress through the cell cycle. As the cells stop dividing and differentiate in Gl, it is the part of the control system that operates in G1 that is most likely to be relevant. In principle, the components of the cell-cycle control system could be components of the timer. The timer, for example, could depend on a decrease in one or more positive intracellular regulators, such as a cyclin or a Cdk... 

Inhibition of cell death. Programmed cell death (apoptosis) is used by organisms to eliminate damaged cells. Inhibition of this process can allow cells with damage to the cell cycle control system to proliferate. 

The cells of the human body can divide to the extent of many millions per second During this process the DNA in each cell must be replicated perfectly so each daughter cell is identical to the parent cell. Moreover, the rate of cell division must be balanced with the need for new cells to replace the dying cells. If insufficient cells are produced the tissue will atrophy. If cells are produced at an excessive rate, a tumour is produced. Eukaryotic cells regulate the process of cell division using a sequence of regulatory proteins in the cell-cycle control system. 

Xenopus oocytes and embryos present a model system for understanding the interface between cell cycle controls and developmental decisions. Maturation of... 

The Ubiquitin System and Some of Its Roles in Cell Cycle Control... 

In addition to cell migration, another characteristic function of the VSM synthetic phenotype is proliferation. CaMKII has been implicated in cell cycle control in a number of systems, but investigations in this area have yield mixed results. Most studies to date have relied on pharmacological inhibitors of CaMKII such as KN-62 or KN-93 (Tombes et al. 1995) and point to a positive role for CaMKII in mediating the cell cycle. Conversely, overexpression of a constitutively active mutant of CaMKIIa. suggested a negative role for kinase (Beauman et al. 2003). Interpretation of the latter studies is complicated by potential nonspecific effects... 

Kohn, K. W. 1999. Molecular interaction map of the mammalian cell cycle control and DNA repair systems. Molec Biol Cell 10 2703-34. 

Diverse Experimental Systems Have Been Used to Identify and Isolate Cell-Cycle Control Proteins... 

Some tours deforce of these methods have been presented in several publications, (see [6,7] and references therein). The studies of Tyson and coworkers are focused on the kinetic analysis of the budding yeast cell cycle. The molecular mechanism of cell cycle control is known in more detail for budding yeast, Saccharomyces cerevisiae, than for any other eukaryotic organism. Many experiments have been done on this system over many years there are about 125 references cited in [6]. The biological details are second to stressing the enormity of this task. The model has nearly twenty variables and that many kinetic equations, and there are about fifty parameters (rate coefficients, binding constants, thresholds, relative efficiencies). A fair number of assumptions need to be made in the cases of absence of any substantiating experimental evidence, and a fair number of approximations need to be made to simplify the kinetic equations. The complexity of this system is indicated in fig. 13.3 and its caption. 

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