Cell proliferation: oncogenes regulation

Normal cellular gene, usually concerned with the regulation of cell proliferation that can be converted to a cancer promoting oncogene by mutation. 

Since then, a plethora of tyrosine-phosphorylated proteins has been discovered. Originally, tyrosine phosphorylation was believed to be involved primarily in regulating cell proliferation, since many oncogene products and growth factor receptors are protein tyrosine kinases (PTKs). However, it has become clear that tyrosine phosphorylation is involved in regulating a variety of cellular processes. In fact, the nervous system contains a large variety of PTKs and protein tyrosine phosphatases (PTPs), and some of these are exclusively expressed in neuronal tissues. Figure 24-1 shows the... 

Finally, inappropriate expression of nuclear transcription factors can lead to cell transformation. For example, the products of he,fos and myc proto-oncogenes are transcription factors that regulate the expression of proteins that promote progression through the cell cycle. Levels of the Fos and Myc proteins are tightly regulated in normal cells. Uncontrolled expression of these proteins leads to cell proliferation. 

Figure 3. Oncogenic potential of ubiquitin ligases. MDM2 and Skp2 regulate levels of the tumor suppressors p53 and p27, respectively. Deregulated degradation of p53 and p27 results in cyclin E/cdk2 activation and cell proliferation.

Oncogene products assume specific locations within the cell. Usually they are associated with one of two locations The plasma membrane or the nucleus. This specificity is consistent with the hypothesis that oncogene products are associated with normal cellular metabolism relating to regulation of cell proliferation it seems likely that many of the elements regulating cell proliferation would be found at the membrane and nucleus of the cell. 

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