XSip1 neuralizing activity involves the co-repressor CtBP and occurs through BMP dependent and independent mechanisms

Abstract

The DNA-binding transcription factor Smad-interacting protein-1 (Sip1) (also named Zfhx1b/ZEB2) plays essential roles in vertebrate embryogenesis. In Xenopus, XSip1 is essential at the gastrula stage for neural tissue formation, but the precise molecular mechanisms that underlie this process have not been fully identified yet. Here we show that XSip1 functions as a transcriptional repressor during neural induction. We observed that constitutive activation of BMP signaling prevents neural induction by XSip1 but not the inhibition of several epidermal genes. We provide evidence that XSip1 binds directly to the BMP4 proximal promoter and modulates its activity. Finally, by deletion and mutational analysis, we show that XSip1 possesses multiple repression domains and that CtBPs contribute to its repression activity. Consistent with this, interference with XCtBP function reduced XSip1 neuralizing activity. These results suggest that Sip1 acts in neural tissue formation through direct repression of BMP4 but that BMP-independent mechanisms are involved as well. Our data also provide the first demonstration of the importance of CtBP binding in Sip1 transcriptional activity in vivo.

Evolutionary functional analysis and molecular regulation of the ZEB transcription factors

“…This further emphasizes the importance of CtBP. Depleting CtBP levels in neuronal precursors in vivo abolished neurulation [74]. Interestingly, induction of the neuronal markers N-CAM (Neural Cell Adhesion Molecule) and NRP (Neuropilin 1) does not seem to depend on the CtBP domain of ZEB2, since deletion of the N-terminal domain could abolish upregulation of these genes.…”

“…Additional experiments showed that ZEB2 functionality as a repressor depends on its deacetylase activity. Inhibition of HDAC by Trichostatin A treatment abrogated ZEB2-mediated neurulation in the Xenopus embryo [74]. Because both the NuRD complex and the cofactor CtBP have been shown to interact with HDAC, the cellular context selecting the proper deacetylase complex remains to be investigated.…”

Transcriptional repressor ZEB2 promotes terminal differentiation of CD8+ effector and memory T cell populations during infection

“…ZEB2 is a two-handed zinc-finger transcription factor and one of two members of the ZEB family in vertebrates; ZEB1 and -2 bind DNA at tandem, separated ) consensus E-box sites (Sekido et al, 1994) and may be in direct competition for E-protein-binding sites. ZEB2 can also mediate transcriptional repression via cooperation with activated Smads or through recruitment of the corepressor CtBP as well as histone deacetylase complexes, particularly NuRD (Verschueren et al, 1999;Postigo and Dean, 1999b;van Grunsven et al, 2007;Verstappen et al, 2008).The role of ZEB proteins in mature T cell function has not previously been investigated. However, Goossens et al (2015) recently found that ZEB2 drives immature T cell lymphoblastic leukemia in humans and mice, and in the mouse model this is caused by enhanced leukemia initiation potential and induction of CD127 expression.…”

“…ZEB2 is a two-handed zinc-finger transcription factor and one of two members of the ZEB family in vertebrates; ZEB1 and -2 bind DNA at tandem, separated ) consensus E-box sites (Sekido et al, 1994) and may be in direct competition for E-protein-binding sites. ZEB2 can also mediate transcriptional repression via cooperation with activated Smads or through recruitment of the corepressor CtBP as well as histone deacetylase complexes, particularly NuRD (Verschueren et al, 1999;Postigo and Dean, 1999b;van Grunsven et al, 2007;Verstappen et al, 2008).…”

Hematology - Science and Practice

“…Each Zn-finger cluster independently can bind a 5'-CACCT(G)-3' sequence located in the target promotor region . The domains outside the Zn-finger clusters seem less conserved and may be essential for the recruitment of various co-repressors, like CtBP (Grooteclaes & Frisch, 2000;Postigo & Dean, 1999b;van Grunsven et al, 2007) or co-activators like p300 or P/CAF (van Grunsven et al, 2006). Still a lot of controversy exists over whether Zeb proteins can only act as transcriptional repressors or as well as activators.…”