The CXXC Zn binding motifs of the human papillomavirus type 16 E7 oncoprotein are not required for its in vitro transforming activity in rodent cells

Braspenning, Joris; Marchini, Antonio; Albarani, Valentina; Lévy, Laurence; Ciccolini, Francesca; Cremonesi, Caterina; Ralston, Robert R.; Gissmann, Lutz; Tommasino, Massimo

doi:10.1038/sj.onc.1201617

Cited by 13 publications

(10 citation statements)

References 15 publications

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“…The coordinated zinc ions are not directly involved in the E7 dimerization (Figure 3c) yet they are reported to be essential for that process (McIntyre et al, 1993;Braspenning et al, 1998;Clements et al, 2000;Alonso et al, 2002). Ethylenediaminetetraacetate led to the disappearance of disperse amide resonances in 1 H-15 N HSQC spectra of HPV45 E7 (data not shown) indicating that removal of zinc causes unfolding of the CR3 region.…”

Section: E7 Interaction With P21 Cip1mentioning

confidence: 98%

“…The C-terminal region of E7 (CR3) contains two CXXC zinc-binding motifs separated by 29 residues (Barbosa et al, 1989). CR3 is responsible for the zinc-dependent dimerization (McIntyre et al, 1993;Braspenning et al, 1998;Clements et al, 2000;Alonso et al, 2002) and for (co-) mediating the interaction of E7 with a large number of diverse cellular proteins involved in the regulation of cell cycle progression and apoptosis, among them pRb and the cyclin-dependent kinase inhibitor (CDKI) p21 CIP1 (Zwerschke and Jansen-Durr, 2000;Munger et al, 2001). p21 CIP1 is the prototypical member of the CIP/KIP family of CDKIs, which share significant sequence homology in their N-terminal cyclin-CDK-binding domains.…”

Section: Introductionmentioning

confidence: 99%

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Solution structure of the partially folded high-risk human papilloma virus 45 oncoprotein E7

et al. 2006

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The oncoprotein E7 of human papilloma viruses (HPV) is involved in the pathogenesis and maintenance of human cervical cancers. The most prevalent HPV types found in cervix carcinomas are HPV16, 18 and 45. The structure of the E7 dimer from HPV45 (PDB 2F8B) was determined by nuclear magnetic resonance spectroscopy. Each monomer comprises an unfolded N-terminus and a well-structured C-terminal domain with a b1b2a1b3a2 topology representing a unique zinc-binding fold found only for E7. Dimerization occurs through the a1/a1 0 helices and intermolecular b-sheet formation but excludes the zinc-binding sites. E7 is reported to interact with a number of cellular proteins (e.g. pRb, p21 CIP1 ). Binding of a peptide derived from the C-terminus of p21CIP1 to the Cterminal domain of E7 was characterized by monitoring chemical shift perturbations of the amide groups of E7. This provides direct evidence that a shallow groove situated between a1 and b1 of the E7 C-terminal domain is interacting with the C-terminus of p21 CIP1. Intriguingly, this binding site overlaps with the low-affinity binding site on E7 for the C-domain of pRb.

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Section: E7 Interaction With P21 Cip1mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Solution structure of the partially folded high-risk human papilloma virus 45 oncoprotein E7

et al. 2006

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“…Previous studies on the E7 proteins of HPV16 and HPV18 have indicated that the C terminus is required to maintain a stable and functional structure of the protein (9,13,34,51). CR3 contains two Cys-X-X-Cys motifs necessary for zinc binding and subsequent folding of the protomer into a unique viral ␤1␤2␣1␤3␣2 topology.…”

Section: Discussionmentioning

confidence: 99%

Systematic Analysis of the Amino Acid Residues of Human Papillomavirus Type 16 E7 Conserved Region 3 Involved in Dimerization and Transformation

Todorović

Massimi

Hung

et al. 2011

J Virol

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The human papillomavirus (HPV) E7 oncoprotein exists as a dimer and acts by binding to many cellular factors, preventing or retargeting their function and thereby making the infected cell conducive for viral replication. Dimerization of E7 is attributed primarily to the C-terminal domain, referred to as conserved region 3 (CR3). CR3 is highly structured and is necessary for E7's transformation ability. It is also required for binding of numerous E7 cellular targets. To systematically analyze the molecular mechanisms by which HPV16 E7 CR3 contributes to carcinogenesis, we created a comprehensive panel of mutations in residues predicted to be exposed on the surface of CR3. We analyzed our novel collection of mutants, as well as mutants targeting predicted hydrophobic core residues of the dimer, for the ability to dimerize. The same set of mutants was also assessed functionally for transformation capability in a baby rat kidney cell assay in conjugation with activated ras. We show that some mutants of HPV16 E7 CR3 failed to dimerize yet were still able to transform baby rat kidney cells. Our results identify several novel E7 mutants that abrogate transformation and also indicate that E7 does not need to exist as a stable dimer in order to transform cells.More than 100 human papillomavirus (HPV) types have been described, and more are presumed to exist (16). HPVs induce papillomas in the cutaneous and mucosal epithelia, where specific HPV types often preferentially infect distinct anatomical sites. HPVs associated with lesions that can progress to carcinogenesis are classified as "high-risk" types, the most common of which is HPV16. In contrast, HPVs associated with benign warts that regress with time are termed "lowrisk" viruses (50). Persistent infection by high-risk HPVs is associated with 99.7% of all human cervical cancer cases (15), other genitourinary cancers, and an increasingly growing number of oral cancers (21).The viral E6 and E7 oncoproteins are consistently expressed in HPV-induced cancers and are necessary to maintain malignant cell growth (3,6,29,42,43). Repression of their transcription by reexpression of the viral E2 protein induces rapid growth arrest and senescence of cervical cancer cells (22,23). The HPV E7 oncoprotein binds the product of the retinoblastoma susceptibility locus (pRb) and the related family members p107 and p130 (17). These proteins function as tumor suppressors, maintaining control of the G 1 /S checkpoint of the cell cycle by binding to the E2F family of transcription factors and by recruiting transcriptional repressor complexes to the E2F-responsive genes (10, 36). Besides pRb, the E7 oncoproteins from high-risk HPV types abrogate the inhibitory activities of the cyclin-dependent kinase inhibitors p21 and p27 by directly binding these factors (19,48). E7 interacts with the pCAF acetyltransferase, the Mi2␤ subunit of the NuRD histone deacetylase complex, the S4 component of the 26S proteasome, the HIF-1␣ and E2F6 transcription factors, and many other important cellular protei...

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“…Such motifs have been previously described in members of the thioredoxin family, in DNA methyltransferase 1, CpG-binding protein, methyl-binding protein, and trithorax/ALL-1/ MLL (Ma et al, 1993;Bestor and Verdine, 1994;Hendrich and Bird, 1998;Voo et al, 2000). CXXC motifs, which like zinc and RING fingers, can also coordinate zinc atoms, are involved in the catalysis of redox reactions by thiol : disulfide oxidoreductases and in the maintenance of protein conformation and homodimerization (Chivers et al, 1996(Chivers et al, , 1997Braspenning et al, 1998;Collet et al, 2003;Fomenko and Gladyshev, 2003).…”

Section: Onzin Is Highly Conserved and Its Expression Is Tissue-restrmentioning

confidence: 99%

Onzin, a c-Myc-repressed target, promotes survival and transformation by modulating the Akt–Mdm2–p53 pathway

et al. 2005

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The c-Myc oncoprotein is a general transcription factor whose target genes dictate the c-Myc phenotype. One such target of c-Myc, 'onzin', is normally expressed at high levels in myeloid cells and is dramatically downregulated in response to c-Myc overexpression. We show here that short hairpin interfering RNA-mediated knockdown of endogenous onzin results in a reduced growth rate and a proapoptotic phenotype. In contrast, onzin overexpression in fibroblasts is associated with an increased growth rate, resistance to apoptotic stimuli, loss of the G2/M checkpoint, and tumorigenic conversion. Onzin-overexpressing cells fail to induce p53 in response to apoptotic stimuli and contain higher levels of the active, phosphorylated forms of Akt1 and, more strikingly, of Mdm2. Using yeast two-hybrid and coimmunoprecipitation assays, we show that onzin directly interacts with both proteins. Green fluorescent protein tagging also confirms directly that Akt1 and Mdm2 colocalize with onzin, although the precise subcellular distribution of each protein is dependent on its relative abundance. Collectively, our results identify onzin as a novel regulator of several p53-dependent aspects of the c-Myc phenotype via its dramatic effect on Mdm2. This is reminiscent of the c-Mycp19 ARF -| Mdm2 pathway and might function as a complementary arm to ensure the proper cellular response to oncogenic and/or apoptotic stimuli.

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The CXXC Zn binding motifs of the human papillomavirus type 16 E7 oncoprotein are not required for its in vitro transforming activity in rodent cells

Cited by 13 publications

References 15 publications

Solution structure of the partially folded high-risk human papilloma virus 45 oncoprotein E7

Solution structure of the partially folded high-risk human papilloma virus 45 oncoprotein E7

Systematic Analysis of the Amino Acid Residues of Human Papillomavirus Type 16 E7 Conserved Region 3 Involved in Dimerization and Transformation

Onzin, a c-Myc-repressed target, promotes survival and transformation by modulating the Akt–Mdm2–p53 pathway

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