The retroviral transforming gene v-myb encodes a 45,000-Mr nuclear transforming protein (p45v-myb). p45v-myb is a truncated and mutated version of a 75,000-Mr protein encoded by the chicken c-myb gene (p75c-myb). Like its viral counterpart, p75c-myb is located in the cell nucleus. As a first step in identifying nuclear targets involved in cellular transformation by v-myb and in c-myb function, we determined the subnuclear locations of p45v-myb and p75c-myb. Approximately 80 to 90% of the total p45v-myb and p75c-myb present in nuclei was released from nuclei at low salt concentrations, exhibited DNA-binding activity, and was attached to nucleoprotein particles when released from the nuclei after digestion with nuclease. A minor portion of approximately 10 to 20% of the total p45v-myb and p75c-myb remained tightly associated with the nuclei even in the presence of 2 M NaCl. These observations suggest that both proteins are associated with two nuclear substructures tentatively identified as the chromatin and the nuclear matrix. The function of myb proteins may therefore depend on interactions with several nuclear targets.
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机译：逆转录病毒转化基因v-myb编码45,000-Mr核转化蛋白（p45v-myb）。 p45v-myb是鸡c-myb基因（p75c-myb）编码的75,000-Mr蛋白的截短和突变版本。像其病毒对应物一样，p75c-myb位于细胞核中。作为鉴定通过v-myb和c-myb功能参与细胞转化的核靶标的第一步，我们确定了p45v-myb和p75c-myb的亚核位置。存在于细胞核中的全部p45v-myb和p75c-myb的大约80％至90％在低盐浓度下从细胞核中释放出来，具有DNA结合活性，并在用核酸酶消化后从细胞核中释放出来时附着在核蛋白颗粒上。即使在存在2 M NaCl的情况下，总p45v-myb和p75c-myb的约10％至20％的一小部分仍与核紧密结合。这些观察结果表明，这两种蛋白都与两个核亚结构相关联，初步确定为染色质和核基质。因此，myb蛋白的功能可能取决于与几个核靶标的相互作用。
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