Favre-Young H, Dif F, Roussille F, Demeneix B A, Kelly P A, Edery M, de Luze A
INSERM Unité 344, Endocrinologie Moléculaire, Faculté de Médecine Necker, Paris, France.
Mol Endocrinol. 2000 Sep;14(9):1411-24. doi: 10.1210/mend.14.9.0525.
PRL and T3 are involved in antagonistic regulations during various developmental processes in vertebrate species. We have studied cross-talk between transcription factors activated by these signaling pathways, i.e. signal transducer and activator of transcription 5 (Stat5) and thyroid hormone receptor beta1 (TRbeta1). Liganded TRbeta1 in the presence of its heterodimeric partner, retinoid X receptor gamma (RXRgamma), inhibited the PRL-induced Stat5a- and Stat5b-dependent reporter gene expression by up to 60%. This T3-inhibitory effect studied on Stat5 activity was partly reversed by overexpression of a TRbeta1 dominant negative variant mutated within its nuclear localization signal (TR2A). We next showed that TRbeta1 and TR2A in the presence of RXRgamma increased and decreased, respectively, Stat5 localization into the nucleus regardless of hormonal stimulation. Thus, our data suggest that TRbeta1 can be associated with Stat5 in the cytoplasm and may be involved in Stat5 nuclear translocation. In PRL-treated cells overexpressing TRbeta1/RXRgamma, both Stat5 and TRbeta1 were coimmunoprecipitated, indicating physical association of the two transcription factors. In these cells, addition of T3 with ovine (o)PRL decreased the amounts of total and tyrosine-phosphorylated Stat5 in the cytoplasm compared with oPRL-treated cells. In the nucleus, no clear difference was observed on Stat5 DNA-binding after treatment with PRL and T3 vs. PRL alone in TRbeta1/RXRgamma transfected cells. However, antibodies directed against TRbeta1 lowered Stat5-DNA binding and addition of the deacetylase inhibitor trichostatin A (TSA) relieved T3 inhibition on Stat5 transcriptional activity. Thus, we postulated that the negative cross-talk between TR and Stat5 on target genes could involve histone deacetylase recruitment by liganded TRbeta1.
催乳素（PRL）和三碘甲状腺原氨酸（T3）参与脊椎动物物种各种发育过程中的拮抗调节。我们研究了由这些信号通路激活的转录因子之间的相互作用，即信号转导子和转录激活子5（Stat5）以及甲状腺激素受体β1（TRβ1）。与维甲酸X受体γ（RXRγ）形成异二聚体的配体化TRβ1，可将PRL诱导的Stat5a和Stat5b依赖性报告基因表达抑制高达60%。对Stat5活性的这种T3抑制作用，可通过在其核定位信号内发生突变的TRβ1显性负变体（TR2A）的过表达部分逆转。接下来我们发现，在有RXRγ存在的情况下，TRβ1和TR2A分别增加和减少Stat5进入细胞核的定位，而与激素刺激无关。因此，我们的数据表明，TRβ1可能在细胞质中与Stat5相关联，并可能参与Stat5的核转位。在过表达TRβ1/RXRγ的PRL处理细胞中，Stat5和TRβ1都被共免疫沉淀，表明这两种转录因子存在物理关联。在这些细胞中，与仅用羊催乳素（o）PRL处理的细胞相比，添加T3和oPRL可降低细胞质中总Stat5和酪氨酸磷酸化Stat5的量。在细胞核中，在TRβ1/RXRγ转染细胞中，用PRL和T3处理后与仅用PRL处理相比，Stat5与DNA的结合没有明显差异。然而，针对TRβ1的抗体降低了Stat5与DNA的结合，并且添加去乙酰化酶抑制剂曲古抑菌素A（TSA）可缓解T3对Stat5转录活性的抑制。因此，我们推测TR和Stat5在靶基因上的负向相互作用可能涉及配体化TRβ1募集组蛋白去乙酰化酶。
