Roche S E, Rio D C
Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3204, USA.
Genetics. 1998 Aug;149(4):1839-55. doi: 10.1093/genetics/149.4.1839.
Drosophila P-element transposition is regulated by a maternally inherited state known as P cytotype. An important aspect of P cytotype is transcriptional repression of the P-element promoter. P cytotype can also repress non-P-element promoters within P-element ends, suggesting that P cytotype repression might involve chromatin-based transcriptional silencing. To learn more about the role of chromatin in P cytotype repression, we have been studying the P strain Lk-P(1A). This strain contains two full-length P elements inserted in the heterochromatic telomere-associated sequences (TAS elements) at cytological location 1A. Mutations in the Polycomb group gene (Pc-G gene), Enhancer of zeste (E(z)), whose protein product binds at 1A, resulted in a loss of Lk-P(1A) cytotype control. E(z) mutations also affected the trans-silencing of heterologous promoters between P-element termini by P-element transgenes inserted in the TAS repeats. These data suggest that pairing interactions between P elements, resulting in exchange of chromatin structures, may be a mechanism for controlling the expression and activity of P elements.
果蝇P因子转座受一种称为P细胞型的母系遗传状态调控。P细胞型的一个重要方面是P因子启动子的转录抑制。P细胞型还能抑制P因子末端内的非P因子启动子，这表明P细胞型抑制可能涉及基于染色质的转录沉默。为了更多地了解染色质在P细胞型抑制中的作用，我们一直在研究P品系Lk-P(1A)。该品系在细胞学位置1A的异染色质端粒相关序列（TAS元件）中插入了两个全长P因子。多梳组基因（Pc-G基因）zeste增强子（E(z)）发生突变，其蛋白质产物在1A处结合，导致Lk-P(1A)细胞型控制丧失。E(z)突变还影响了插入TAS重复序列中的P因子转基因对P因子末端之间异源启动子的反式沉默。这些数据表明，P因子之间的配对相互作用导致染色质结构交换，可能是控制P因子表达和活性的一种机制。
