 These include the gag-onc fusion protein, rex, tax, v-fms, ras, v-myc, v-src, v-akt, v-cbl, v-crk, v-maf, v-abl, v-erbA, v-erbB, v-fos, v-mos, v-myb, v-raf, v-rel, and v-sis.The "v" prefix indicates viral genes which once originated as similarly named genes of the host species, but have since been altered through independent evolution as retroviral components.Not all retroviral proteins are oncogenic.