Transposable Elements and Cancer
Tumor progression is accompanied by many chromosomal aberrations and DNA rearrangements which contribute to the aggressiveness of the tumor. It is possible that active transposition of DNA elements play a role in these events. Approximately one third of the mammalian genome is composed of repetitive sequences (103 — 105 copies). This includes endogeneous retrovirus-like elements as well as short (SINE) and long (LINE) interdispersed DNA elements (Singer 1982; Singer 1982). The features of these elements is given in Fig. 1. Some of these features may suggest that they can behave as mobile elements and therefore may be adequate candidates for transposition in tumors. By integration near oncogenes or related genes these elements may affect the activity of such genes. One example for such an event was provided by the transposition of the intracisternal A-particle genome near the oncogene c-mos in mouse plasmacytoma (Rechavi et al 1982; Kuff et al 1983; Canaani et al 1983). Since then several additional examples of IAP transposition near cellular genes were described (Table 1). As a result of these transpositions the expression of the cellular genes was affected (Table 1) and in the case of c-mos the activated gene transformed NIH 3T3 cells. These examples prompted us to look in various tumors for oncogenes rearrangement and to search if other repetitive elements may also be transposed.
KeywordsDirect Repeat Active Transposition Cellular Oncogene Canine Transmissible Venereal Tumor Transmissible Venereal Tumor
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