CPP‐E1A fusion peptides inhibit CtBP‐mediated transcriptional repression

Abstract

The carboxyl‐terminal binding proteins (CtBP) are transcriptional corepressors that regulate the expression of multiple epithelial‐specific and pro‐apoptotic genes. Overexpression of CtBP occurs in many human cancers where they promote the epithelial‐to‐mesenchymal transition, stem cell‐like features, and cell survival, while knockdown of CtBP in tumor cells results in p53‐independent apoptosis. CtBPs are recruited to their target genes by binding to a conserved PXDLS peptide motif present in multiple DNA‐binding transcription factors. Disrupting the interaction between CtBP and its transcription factor partners may be a means of altering CtBP‐mediated transcriptional repression and a potential approach for cancer therapies. However, small molecules targeting protein–protein interactions have traditionally been difficult to identify. In this study, we took advantage of the fact that CtBP binds to a conserved peptide motif to explore the feasibility of using peptides containing the PXDLS motif fused to cell‐penetrating peptides (CPP) to inhibit CtBP function. We demonstrate that these peptides disrupt the ability of CtBP to interact with its protein partner, E1A, in an AlphaScreen assay. Moreover, these peptides can enter both lung carcinoma and melanoma cells, disrupt the interaction between CtBP and a transcription factor partner, and inhibit CtBP‐mediated transcriptional repression. Finally, the constitutive expression of one such peptide, Pep1‐E1A‐WT, in a melanoma cell line reverses CtBP‐mediated oncogenic phenotypes including proliferation, migration, and sphere formation and limits tumor growth in vivo. Together, our results suggest that CPP‐fused PXDLS‐containing peptides can potentially be developed into a research tool or therapeutic agent targeting CtBP‐mediated transcriptional events in various biological pathways.

Inflammation‐dependent overexpression of c‐Myc enhances CRL4DCAF4 E3 ligase activity and promotes ubiquitination of ST7 in colitis‐associated cancer

“…Immunoblot analysis was performed as described previously , and details are provided in supplementary material, Supplementary materials and methods.…”

The C-terminal of the E1A binding protein 2 enhances the metastatic potential of keratinocyte-derived cutaneous squamous carcinoma cells via the gp130/JAK2/Stat1 signaling pathway

“…Previous studies have demonstrated that CtBP acts as a transcriptional co-repressor, whereas quite a few studies have exposed context-specific of CtBPs in transcriptional activation [12]. For instance, CtBP2 has been shown to increase the expression level of Tiam1 in an NADH-dependent manner, and to activate the transcription factor 4 signaling pathway [29,30].…”

“…The significance of the CtBP co-repressor composite in manifold developmental processes implies that the dysregulation of CtBPs expression in certain human tissues may be involved in oncogenesis [6]. Additionally, recent study implied that the CtBP protein was frequently hyper-activated in various types of tumor cells [12]. It is previously exposed that CtBPs comprise amino acid sequence homology with NADH-dependent dehydrogenases.…”

C-terminal binding proteins 1 and 2 in traumatic brain injury-induced inflammation and their inhibition as an approach for anti-inflammatory treatment

“…We have shown previously that the Pep1-E1A peptide disrupts the interaction of CtBP1 with the PLDLS-containing repressor ZEB1 in cancer cells and relieves the transcriptional repression of CDH1 (E-cadherin) and BAX by the CtBPs (Blevins et al, 2018). To explore whether this peptide inhibitor can interfere with the transactivation function of CtBP1 and CtBP2, we preincubated Pep1-E1A with mouse primary microglia and astrocytes for 2 h prior to stimulation with LPS and measured mRNA levels of the above nine CtBP-regulated proinflammatory genes by RT-qPCR.…”