Lombardi Maria, Castoria Gabriella, Migliaccio Antimo, Barone Maria Vittoria, Di Stasio Rosina, Ciociola Alessandra, Bottero Daniela, Yamaguchi Hiroshi, Appella Ettore, Auricchio Ferdinando
Dipartimento di Patologia Generale, Il Università di Napoli, 80138 Naples, Italy.
J Cell Biol. 2008 Jul 28;182(2):327-40. doi: 10.1083/jcb.200712125. Epub 2008 Jul 21.
In breast cancer cells, cytoplasmic localization of the estradiol receptor alpha (ERalpha) regulates estradiol-dependent S phase entry. We identified a nuclear export sequence (NES) in ERalpha and show that its export is dependent on both estradiol-mediated phosphatidylinositol-3-kinase (PI3K)/AKT activation and chromosome region maintenance 1 (CRM1). A Tat peptide containing the ERalpha NES disrupts ERalpha-CRM1 interaction and prevents nuclear export of ERalpha- and estradiol-induced DNA synthesis. NES-ERalpha mutants do not exit the nucleus and inhibit estradiol-induced S phase entry; ERalpha-dependent transcription is normal. ERalpha is associated with Forkhead proteins in the nucleus, and estradiol stimulates nuclear exit of both proteins. ERalpha knockdown or ERalpha NES mutations prevent ERalpha and Forkhead nuclear export. A mutant of forkhead in rhabdomyosarcoma (FKHR), which cannot be phosphorylated by estradiol-activated AKT, does not associate with ERalpha and is trapped in the nucleus, blocking S phase entry. In conclusion, estradiol-induced AKT-dependent phosphorylation of FKHR drives its association with ERalpha, thereby triggering complex export from the nucleus necessary for initiation of DNA synthesis and S phase entry.
在乳腺癌细胞中，雌激素受体α（ERα）的细胞质定位调节雌激素依赖的S期进入。我们在ERα中鉴定出一个核输出序列（NES），并表明其输出依赖于雌激素介导的磷脂酰肌醇-3激酶（PI3K）/AKT激活以及染色体区域维持蛋白1（CRM1）。包含ERα NES的Tat肽破坏ERα-CRM1相互作用，并阻止ERα和雌激素诱导的DNA合成的核输出。NES-ERα突变体不会离开细胞核，并抑制雌激素诱导的S期进入；ERα依赖的转录是正常的。ERα在细胞核中与叉头蛋白相关联，雌激素刺激这两种蛋白的核输出。ERα敲低或ERα NES突变会阻止ERα和叉头蛋白的核输出。横纹肌肉瘤中叉头蛋白（FKHR）的一个突变体不能被雌激素激活的AKT磷酸化，它不与ERα相关联，并被困在细胞核中，从而阻止S期进入。总之，雌激素诱导的FKHR的AKT依赖磷酸化驱动其与ERα的关联，从而触发DNA合成起始和S期进入所必需的复合物从细胞核中输出。
