Characterization of p73 functional domains necessary for transactivation and growth suppression

Nozell, Susan E.; Wu, Yijun; McNaughton, Kelly; Liu, Gang; Willis, Amy; Paik, Jason C.; Chen, Xinbin

doi:10.1038/sj.onc.1206470

Cited by 37 publications

(28 citation statements)

References 45 publications

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“…p63 and p73 share a high similarity to p53, especially in their DNA-binding domains, and transactivate many p53 targets, such as p21 and MDM2 (29,34). Thus, we examined whether p63 and p73 regulate ECT2 expression.…”

Section: Resultsmentioning

confidence: 99%

The Epithelial Cell Transforming Sequence 2, a Guanine Nucleotide Exchange Factor for Rho GTPases, Is Repressed by p53 via Protein Methyltransferases and Is Required for G1-S Transition

Scoumanne

Chen

2006

Cancer Research

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The epithelial cell transforming sequence 2 (ECT2), a member of the Dbl family of guanine nucleotide exchange factor for Rho GTPases, is required for cytokinesis. The tumor suppressor p53 plays a crucial role in coordinating cellular processes, such as cell cycle arrest and apoptosis, in response to stress signals. Here, we showed that ECT2 is negatively regulated by wild-type p53 but not tumor-derived mutant p53 or other p53 family members. In addition, ECT2 is down-regulated in multiple cell lines by DNA damage agents and Nutlin-3, an MDM2 antagonist, in a p53-dependent manner. We also showed that the activity of the ECT2 promoter is repressed by wild-type p53, and to a lesser extent, by p21. In addition, the second activation domain in p53 is necessary for the efficient repression of ECT2. Importantly, we found that the ECT2 gene is bound by p53 in vivo in response to DNA damage and Nutlin-3 treatment. Furthermore, we provided evidence that inhibition of protein methyltransferases, especially arginine methyltransferases, relieve the repression of ECT2 induced by DNA damage or Nutlin-3 in a p53-dependent manner. Finally, we generated multiple cell lines in which ECT2 is inducibly knocked down and found that ECT2 knockdown triggers cell cycle arrest in G 1 . Taken together, we uncovered a novel function for ECT2 and provided a novel mechanism by which p53 represses gene expression via protein methyltransferases. (Cancer Res 2006; 66(12): 6271-9)

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Section: Resultsmentioning

confidence: 99%

The Epithelial Cell Transforming Sequence 2, a Guanine Nucleotide Exchange Factor for Rho GTPases, Is Repressed by p53 via Protein Methyltransferases and Is Required for G1-S Transition

Scoumanne

Chen

2006

Cancer Research

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“…1A). We showed recently that the level of HA-p73␤ in HA-p73␤-24 cells is sufficient to induce cell cycle arrest and apoptosis (42).…”

Section: Resultsmentioning

confidence: 99%

ΔNp73β Is Active in Transactivation and Growth Suppression

Liu

Nozell

Xiao

et al. 2004

Molecular and Cellular Biology

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109

114

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p73, a p53 family protein, shares significant sequence homolog and functional similarity with p53. However, unlike p53, p73 has at least seven alternatively spliced isoforms with different carboxyl termini (p73␣-). Moreover, the p73 gene can be transcribed from a cryptic promoter located in intron 3, producing seven more proteins (⌬Np73␣-). ⌬Np73, which does not contain the N-terminal activation domain in p73, has been thought to be transcriptionally inactive and dominant negative over p53 or p73. To systemically analyze the activity of the ⌬N variant, we generated stable cell lines, which inducibly express ⌬Np73␣, ⌬Np73␤, and various ⌬Np73␤ mutants by using the tetracycline-inducible expression system. Surprisingly, we found that ⌬Np73␤ is indeed active in inducing cell cycle arrest and apoptosis. Importantly, we found that, when ⌬Np73␤ is expressed at a physiologically relevant level, it is capable of suppressing cell growth. We then demonstrated that these ⌬Np73␤ activities are not cell type specific. We showed that the 13 unique residues at the N terminus are required for ⌬Np73␤ to suppress cell growth. We also found that, among the 13 residues, residues 6 to 10 are critical to ⌬Np73␤ function. Furthermore, we found that ⌬Np73␤ is capable of inducing some p53 target genes, albeit to a lesser extent than does p73␤. Finally, we found that the 13 unique residues, together with the N-terminal PXXP motifs, constitute a novel activation domain. Like ⌬Np73␤, ⌬Np73␥ is active in transactivation. However, unlike ⌬Np73␤, ⌬Np73␣ is inactive in suppressing cell growth. Our data, together with others' previous findings, suggest that ⌬Np73␤ may have distinct functions under certain cellular circumstances.p73, along with p53 and p63, constitutes the p53 family. p73 shares 63% identity in amino acids with p53 in the DNAbinding domain, including all the DNA contact residues, 38% identity in the tetramerization domain, and 29% identity in the transactivation domain (31,37,55). In contrast to the human p53 gene, which is found to only encode one protein, human TP73 produces at least seven alternatively spliced isoforms with different carboxyl termini (p73␣-), termed the TA variant (10,28,38,53). For example, p73␣ is the longest form of the p73 protein, which contains a sterile ␣ motif (SAM domain) and an extreme C-terminal region, whereas p73␤ is a smaller polypeptide, missing the extreme C-terminal region and most of the SAM domain in p73␣ (8,29,31,50). In addition to the alternative splicing in the C terminus, TP73 is also transcribed from a cryptic promoter located in intron 3, which gives rise to at least another seven isoforms (⌬Np73␣-), termed the ⌬N variant (28,55,56,58). The ⌬N variant does not contain the activation domain in p73 due to lack of sequences encoded by exon 2 (45, 56). However, the ⌬N variant acquires 13 unique residues at the N terminus compared with the TA variant (45, 56). Similar to TP73, TP63 encodes both .In addition to the significant sequence homology, p53 and p73 share a lot of functional similar...

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“…Cell Culture-MCF7 cell lines, which inducibly express various isoforms of the p53 family proteins, were cultured as described previously (17,18). RKO-GLX2 cell lines, which inducibly express GLX2 under the control of the tetracyclineinducible promoter, were generated as described previously (19).…”

Section: Methodsmentioning

confidence: 99%

Glyoxalase II, a Detoxifying Enzyme of Glycolysis Byproduct Methylglyoxal and a Target of p63 and p73, Is a Pro-survival Factor of the p53 Family

Chen

2006

Journal of Biological Chemistry

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The p53 family proteins are transcription factors and have both common and distinct functions. p53 is a classic tumor suppressor, whereas p63 and p73 have fundamental functions in development. To gain an insight into the functional diversities among the p53 family, target genes specifically regulated by p63 and p73 were examined. Here, we found that the GLX2 gene, which encodes glyoxalase II enzyme, is up-regulated by p63 and p73. Accordingly, a specific responsive element was found in intron 1 of the GLX2 gene, which can be activated and bound by p63 and p73. We also found that, upon overexpression, the cytosolic, but not the mitochondrial, GLX2 inhibits the apoptotic response of a cell to methylglyoxal, a by-product of glycolysis. Likewise, we showed that cells deficient in GLX2 are hypersensitive to methylglyoxal-induced apoptosis. Interestingly, a deficiency in GLX2 also enhances the susceptibility of a cell to DNA damage-induced apoptosis in a p53-dependent manner. These observations reveal a novel link between the p53 family and the glyoxalase system. Given that methylglyoxal is frequently generated under both physiological and pathological conditions, we postulate that GLX2 serves as a pro-survival factor of the p53 family and plays a critical role in the normal development and in the pathogenesis of various human diseases, including cancer, diabetes, and neurodegenerative diseases.

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Characterization of p73 functional domains necessary for transactivation and growth suppression

Cited by 37 publications

References 45 publications

The Epithelial Cell Transforming Sequence 2, a Guanine Nucleotide Exchange Factor for Rho GTPases, Is Repressed by p53 via Protein Methyltransferases and Is Required for G1-S Transition

The Epithelial Cell Transforming Sequence 2, a Guanine Nucleotide Exchange Factor for Rho GTPases, Is Repressed by p53 via Protein Methyltransferases and Is Required for G1-S Transition

ΔNp73β Is Active in Transactivation and Growth Suppression

Glyoxalase II, a Detoxifying Enzyme of Glycolysis Byproduct Methylglyoxal and a Target of p63 and p73, Is a Pro-survival Factor of the p53 Family

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