NEURL4 regulates the transcriptional activity of tumor suppressor protein p53 by modulating its oligomerization

Abstract

p53 is a transcription factor that regulates important cellular processes related to tumor suppression, including induction of senescence, apoptosis, and DNA repair as well as the inhibition of angiogenesis and cell migration. Therefore, it is critical to understand the molecular mechanism that regulates it. p53 tetramerization is a key step in its activation process and the regulation of this oligomerization, an important control point. The E3 ubiquitin ligase HERC2 controls the p53 transcriptional activity by regulation of its oligomerization state. HERC2-interacting proteins such as the adaptor-like protein with six neuralized domains NEURL4 are also candidates to regulate p53 activity. Here, we demonstrate the existence of an interaction network between NEURL4, HERC2 and p53 proteins. We report a functional interaction between NEURL4 and p53, involving the C-terminal region of p53 and the neuralized domains 3 and 4 of NEURL4. Through this interaction, NEURL4 regulates the transcriptional activity of p53. Thus, NEURL4 depletion reduced the transcriptional activity whereas NEURL4 overexpression increased it. In both cases, p53 stability was not affected. Although NEURL4 may interact with p53 independently of the E3 ubiquitin ligase HERC2, we observed that both proteins are needed to regulate the transcriptional activity of p53. Clonogenic assays confirmed the functional relevance of this interaction observing a decrease in cell growth by NEURL4 overexpression correlated to the increase of cellular cycle inhibitor p21 by p53 activation. Under these conditions, NEURL4 activated p53 oligomerization. All these findings identify NEURL4 as a novel regulator of the p53’s signaling.

Large HERCs Function as Tumor Suppressors

“…The role of the HERC2-NEURL4 complex in activating the tumor suppressor p53 could explain the improved prognosis for cancer patients when levels of HERC2 expression are higher (Figure 1A). According to this model, NEURL4 should also function as a tumor suppressor and in agreement with this, analysis of cancer genomics datasets from the cBioPortal shows a high frequency in NEURL4 deletions in prostate cancer (10).…”

“…The second model emerges from studies performed by Cubillos-Rojas et al (9, 10). Those authors demonstrate how HERC2 regulates p53 activity.…”

Assembly of human C-terminal binding protein (CtBP) into tetramers

“…Assembly of protein components is an important theme in transcriptional regulation (45)(46)(47). A central element of this process is often the oligomerization of one or more individual protein components contributing to transcriptional complex assembly (27,28). In the case of CtBP, strong evidence exists for the role of NAD(H) in both co-transcriptional activity and oligomerization (3,23,25,29,32,33).…”

“…Regulation of gene expression through the oligomerization of transcriptional factors is an important paradigm (27,28). In the case of CtBP, substantial evidence exists that oligomerization is linked with NAD(H) binding (3, 25, 29 -32), and dimerdestabilizing mutants have been found to inhibit transcriptional function (33)(34)(35)(36).…”

HERC Ubiquitin Ligases in Cancer

“…For example, HERC2 controls the transcriptional activity of the tumor suppressor protein p53 [66]. Tetramerization of p53 is a key step in its activation, and this oligomerization process is modulated by a complex formed by NEURL4 and HERC2 [67]. Recently, it has been reported that MDM2 is present in this complex.…”