p150/glued modifies nuclear estrogen receptor function.

Estrogen modulates gene expression through interactions with estrogen receptors (ERs) that bind chromosomal target genes. Recent studies have suggested an interaction between the cytoskeletal system and estrogen signaling; these have implicated a role of cytoplasmic microtubules in scaffolding ERalpha and enhancing nongenomic function; in addition, other experiments demonstrate that dynein light chain 1 may chaperone ERalpha to the nucleus, indirectly increasing transcriptional potency. Actin/myosin and dynein light chain 1 are also required for estrogen-mediated chromosomal movement that is required for transcriptional up-regulation of ERalpha targets. We present evidence that the dynactin component, p150/glued, directly influences the potency of nuclear ER function. Increasing the stoichiometric ratio of p150/glued and ERalpha by overexpression enhances estrogen responses. ERalpha enhancement by p150/glued does not appear to be influenced by shifts in subcellular localization because microtubule disruption fails to increase nuclear ERalpha. Rather, we find that modest amounts of p150/glued reside in the nucleus of cells, suggesting that it plays a direct role in nuclear transcription. Notably, p150/glued is recruited to the pS2 promoter in the presence of hormone, and, in MCF-7 cells, knockdown of p150/glued levels reduces estrogen-dependent transcription. Our results suggest that p150/glued modulates estrogen sensitivity in cells through nuclear mechanisms.