Oncogene Viral

Bais C, Santomasso B, Coso O, et al. G-protein-coupled receptor of Kaposi s sarcoma-associated herpesvirus is a viral oncogene and angiogenesis activator. Nature 1998 391(6662) 86-89. 

Components of Tyrosine Kinase Signal Transduction Cascades Are Discovered as Cellular (or Viral) Oncogenes... 

For example, c-Fos is heavily phosphorylated on a series of serine residues in the C-terminal domain of the protein by several types of protein kinases. The likely functional importance of these phosphorylation sites is indicated by the fact that the difference between c-Fos (the normal cellular form of the protein) and v-Fos (the viral oncogene product) is a frameshift mutation in the v-Fos protein, which obliterates the phosphorylated serine residues. It is speculated that the loss of these phosphorylation sites removes one mechanism by which the cell can regulate the protein, thereby leading to cellular transformation. 

AKT-1 kinase (also called protein kinase B or PKBa) is a serine/threonine kinase belonging to the AGC kinase family [1], AKT was identified from a viral oncogene, v-akt, found in tumor lines established from spontaneous thymomas found in AKR mice [2]. Subsequently, two more AKT isoforms, AKT-2 (or PKB(3) and AKT-3 (or PKBy) have been identified [3]. Reviews exist detailing the structural and cell biology of AKT and the reader is referred to these for further information [4,7,12]. 

Beyond the Hayflick limit, cells that have escaped senescence and/or crisis must progress beyond mortality stage 2 (Figure 26.1). Recent studies have shown that human telomerase reverse transcriptase cDNA (hTERT) in combination with viral oncogenes also has the potential to immortalize human airway epithelial cells [15, 78-82], However, even though hTERT alone will cause enhanced growth potential of a cell line, with the exception of one study [81],... 

Remarkably, viral oncogene relatives are present in normal cells—these are termed proto-oncogenes. Therefore, each cell in the human body carries the potential to become cancerous in the form of its proto-oncogenes, which include myc, ms, myb, fes, fms, fos, and jun. 

The difference between the normal cellular proto-oncogene, c-ras, and the viral oncogene, v-ras, lies in a single base pair change among the 5000 base pairs in this gene. 

IIGI Akt2 -r3 kb (i2) 7A3 Aktl 3/2 Thymoma viral oncogene homolog 2, kinase 1... 

Several cancer cell types are characterized by expressing a truncated EGF receptor. The related viral oncogene, V-er B, also encodes a truncated receptor which lacks most of the extracellular domain (the EGF receptor is also known as C-erbB). Mutant receptors that display inappropriate constitutive activity can lead to cellular transformation, due to the continuous generation of mitogenic signal. 

Src kinase was discovered during the search for the tumor-causing principle of retroviruses. The viral oncogene product of these viruses, v-Src kinase, was the first tyrosine kinase to be identified. In comparison to its cellular coimterpart, c-Src kinase, v-Src lacks the autoinhibitory structural element that controls protein kinase activity. As a consequence of this loss, v-Src kinase is constitutively active and is a potent transforming protein. 

Introduction of viral oncogenes into the host genome... 

Soon after discovery of the oncogene, it was demonstrated that the viral oncogenes are mutated forms of the genes of cellular proteins that are also active in normal cells. The cellular variants of viral oncogenes were named proto-oncogenes. 

FIGURE 12-47 Conversion of a regulatory gene to a viral oncogene. 

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