The transcription co-repressor TLE1 interacted with the intracellular region of gpl30 through its Q domain

Suppression of RND3 activity by AES downregulation promotes cancer cell proliferation and invasion

Amino-terminal enhancer of split (AES) is a member of the Groucho/TLE family. Although it has no DNA-binding site, AES can regulate transcriptional activity by interacting with transcriptional factors. Emerging evidence indicates that AES may play an important role in tumor metastasis, but the molecular mechanism is still poorly understood. In this study, we found that knockdown of AES by RNA interference (RNAi) downregulated RND3 expression at the mRNA and protein levels in MDA-MB-231 and HepG2, two cancer cell lines. Furthermore, luciferase assays showed that overexpression of AES significantly enhanced RND3 promoter activity. Moreover, inhibition of AES both in MDA-MB-231 and HepG2 cells by RNAi significantly promoted cell proliferation, cell cycle progression and invasion, consistent with the effects of RNAi-mediated RND3 knockdown in these cells. For the first time, data are presented showing that alteration of the malignant behavior of cancer cells by AES is related to RND3 regulation, and these findings also provide new insights into the mechanism of AES action in regulating tumor malignancy.

Transducin-like enhancer of Split-1 (TLE1) combines with Forkhead box protein G1 (FoxG1) to promote neuronal survival

Transducin-like enhancer of split-1 (TLE1) plays a critical role in the regulation of neurogenesis by inhibiting the differentiation of neural progenitor cells into neurons. Although TLE1 is also expressed highly in the postnatal brain and through adulthood, its role in postmitotic neurons is not clear. Using cultures of cerebellar granule neurons, we show that expression of TLE1 is reduced in neurons primed to die. Reestablishment of elevated TLE1 levels by ectopic expression protects neurons from death, whereas suppression of TLE1 expression in otherwise healthy neurons induces cell death. These results show that TLE1 is necessary for the maintenance of neuronal survival. Experiments using pharmacological inhibitors as well as expression of point mutants indicate that phosphorylation of TLE1 by casein kinase-2 (CK2) at Ser-239 and Ser-253 is necessary for its survival-promoting activity. TLE1-mediated survival is also inhibited by pharmacological inhibition of PI3K-Akt signaling but not by inhibitors of Raf-MEK-ERK signaling or other molecules, including histone deacetylases, calcium calmodulin kinase, or CK1. The survival-promoting activity of TLE1 depends critically on interaction with FoxG1, another protein involved in the regulation of neurogenesis and shown previously to promote survival of postmitotic neurons. Likewise, the ability of FoxG1 to promote neuronal survival depends on TLE1. Taken together, our study demonstrates that TLE1 cooperates with FoxG1 to promote neuronal survival in a CK2- and PI3K-Akt-dependent manner.

EphrinB1 interacts with the transcriptional co-repressor Groucho/xTLE4

Ephrin signaling is involved in various morphogenetic events, such as axon guidance, hindbrain segmentation, and angiogenesis. We conducted a yeast two-hybrid screen using the intracellular domain (ICD) of EphrinB1 to gain biochemical insightinto the function of the EphrinB1 ICD. We identified the transcriptional co-repressor xTLE1/Groucho as an EphrinB1 interacting protein. Whole-mount in situ hybridization of Xenopus embryos confirmed the co-localization of EphrinB1 and a Xenopus counterpart to TLE1, xTLE4, during various stages of development. The EphrinB1/xTLE4 interaction was confirmed by co-immunoprecipitation experiments. Further characterization of the interaction revealed that the carboxy-terminal PDZ binding motif of EphrinB1 and the SP domain of xTLE4 are required for binding. Additionally, phosphorylation of EphrinB1 by a constitutively activated fibroblast growth factor receptor resulted in loss of the interaction, suggesting that the interaction is modulated by tyrosine phosphorylation of the EphrinB1 ICD.

[Prokaryotic expression and purification of human TLE1 N-terminal Q domain fragment and production of its polyclonal antibody]

背景与目的

TLE1是参与Wnt、Notch以及EGFR信号通路调控的一种重要蛋白。TLE1 N端Q结构域片段通过介导自身寡聚化及与LEF1结合发挥调控作用。本实验旨在构建人TLE1 N端Q区基因在大肠杆菌的融合表达载体，制备并纯化人TLE1 N端Q结构域蛋白片段，制备TLE1 Q结构域多克隆抗体。

方法

以人肺腺癌cDNA库为模板聚合酶链反应（polymerase chain reaction, PCR）特异性扩增TLE1-Q(1-136)基因序列，与pGEX-4T-1质粒连接后转化感受态大肠杆菌E.coli。以异丙基-β-D-硫代半乳糖苷（isopropyl-β-D thiogalactoside, IPTG）诱导表达产生融合蛋白GSTTLE1-Q(1-136)。经亲和层析，Thrombin酶切，FPLC纯化，SDS-PAGE鉴定目的蛋白TLE1-Q(1-136)。免疫家兔，制备多克隆抗体。

结果

测序证实重组表达质粒中的人TLE1 N端Q结构域基因序列正确，成功构建表达型重组质粒pGEX-4T1-TLE1-Q。重组质粒转化大肠杆菌C+后，经诱导，重组蛋白GST-TLE1-Q(1-136)得到表达。SDS-PAGE鉴定示纯化蛋白为目的蛋白人TLE1 N端Q结构域片段TLE1-Q(1-136)。免疫家兔后收获抗血清，ELISA显示抗体效价为1:20 000，具有高度特异性。免疫印迹结果显示，制备的多抗可与TLE1-Q(1-136)蛋白特异性结合。

结论

成功构建了人TLE1 N端Q结构域重组融合蛋白表达质粒pGEX-4T1-TLE1-Q，表达纯化了稳定可溶TLE1 N端Q结构域蛋白TLE1-Q(1-136)，制备了人TLE1 N端Q结构域蛋白片段多克隆抗体，为进一步研究TLE1在肺癌生成中的作用奠定了基础。

The RING-finger domain of the fungal repressor crgA is essential for accurate light regulation of carotenogenesis

Mucor circinelloides responds to blue light by activating the biosynthesis of carotenoids. Gene crgA acts as a repressor of this light-regulated process, as its inactivation leads to overaccumulation of carotenoids in both the dark and the light. The predicted CrgA protein contains different recognizable structural domains, including a RING-finger zinc-binding motif, several glutamine-rich regions, a putative nuclear localization signal and an isoprenylation domain. To gain insight into the specific mode of action of the CrgA protein, we sought to define the CrgA domains critical for the light regulation of carotenogenesis. For this, mutant crgA alleles harbouring missense or deletion mutations in conserved residues of those domains were generated, and their functionality was assessed by testing their ability to complement a null crgA mutation. Point mutations of the amino-terminal RING-finger domain abrogated the ability of CrgA to repress carotenogenesis in the dark, as did the deletion of a poly glutamine-rich region at the carboxyl domain of CrgA. In contrast, mutations of the isoprenylation domain only slightly affected the CrgA function in carotenogenesis. The results identify two functional domains presumably involved in protein-protein interaction in the CrgA protein and suggest a role for the ubiquitin-proteasome pathway in the light regulation of carotenogenesis in fungi.