Most tumor suppressor genes (whose function in cancer biology was surmised by their inactivation or deletion) turn out to be important in normal cell growth and proliferation. Inactivation of these genes opens the gates to malignant transformation driven by aberrant growth signals. In general, tumor suppressor dysfunction does not initiate genomic instability or aneuploidy, hallmarks of the origin of cancer, but they are at least as susceptible as other genes to the consequences of these destabilizing phenomena. On the other hand, these genes have a predilection to inactivation by epigenetic mechanisms, such as aberrant methylation with the progression of cell transformation.
This chapter focuses on the pathways anchored by the two "big" regulators of the cell cycle: p53 and the retinoblastoma (Rb) genes. Until recently the connections between these two networks was obscure (1). It is now apparent that they regulate and counter-regulate each other in a Ying-Yang fashion. The network centred on p53 is denser and more intricate (2,3), receiving signals from upstream modulators and downstream effectors. In addition to their respective roles at crucial check-points in the cell cycle and DNA repair, the products of both these genes appear to have roles in embryogenesis, cell differentiation and cell fate including senesce(1,4,5).
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Achieve Health, Wealth And Body Balance Through Yin Yang Mastery. Cut up on the old stone drums of Republic of China, inscribed in books handed down through thousands of years, traced on ancient saucers and on saucers made today, is a sign and a symbol. It is woven into textiles, stitched into embroideries, emblazoned over house gates, wrought into shop emblems, a circle, locked together inside it yang and yin yang, light, yin, dark, each carrying inside itself the essence of the other, each shaped to the other