Adolf-Butenandt-Institute and Center for Integrated Protein Science, Ludwig-Maximilians-University, D-80336 Munich, Germany.
Mol Cell. 2013 Jul 25;51(2):174-84. doi: 10.1016/j.molcel.2013.06.011.
Dosage compensation in Drosophila involves a global activation of genes on the male X chromosome. The activating complex (MSL-DCC) consists of male-specific-lethal (MSL) proteins and two long, noncoding roX RNAs. The roX RNAs are essential for X-chromosomal targeting, but their contributions to MSL-DCC structure and function are enigmatic. Conceivably, the RNA helicase MLE, itself an MSL subunit, is actively involved in incorporating roX into functional DCC. We determined the secondary structure of roX2 and mapped specific interaction sites for MLE in vitro. Upon addition of ATP, MLE disrupted a functionally important stem loop in roX2. This RNA remodeling enhanced specific ATP-dependent association of MSL2, the core subunit of the MSL-DCC, providing a link between roX and MSL subunits. Probing the conformation of roX in vivo revealed a remodeled stem loop in chromatin-bound roX2. The active remodeling of a stable secondary structure by MLE may constitute a rate-limiting step for MSL-DCC assembly.
在果蝇中，剂量补偿涉及到雄性 X 染色体上基因的全局激活。激活复合物（MSL-DCC）由雄性特异性致死（MSL）蛋白和两个长的非编码 roX RNA 组成。roX RNA 对于 X 染色体靶向是必不可少的，但它们对 MSL-DCC 结构和功能的贡献仍然是个谜。可以想象，RNA 解旋酶 MLE 本身就是 MSL 亚基的一部分，它积极参与将 roX 纳入功能性 DCC 中。我们确定了 roX2 的二级结构，并在体外绘制了 MLE 的特定相互作用位点。加入 ATP 后，MLE 破坏了 roX2 中一个功能重要的茎环。这种 RNA 重塑增强了 MSL-DCC 核心亚基 MSL2 的特定 ATP 依赖性结合，为 roX 和 MSL 亚基之间提供了联系。在体内探测 roX 的构象时，发现染色质结合的 roX2 中的茎环发生了重塑。MLE 对稳定二级结构的主动重塑可能是 MSL-DCC 组装的限速步骤。
