NCoR1 Mediates Papillomavirus E8^E2C Transcriptional Repression

Powell, M; Smith, Jennifer A.; Sowa, Mathew E.; Iftner, Thomas; Stubenrauch, Frank; Howley, Peter M.

doi:10.1128/jvi.02390-09

Cited by 39 publications

(61 citation statements)

References 67 publications

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“…In contrast, the 31E8^E2C protein inhibits the growth of HeLa cells as well as 31E2 (31,38). Growth inhibition by 31E8^E2C was correlated with a reduction of E6/E7 transcripts and the induction of p53, p21, and pRb proteins (38).…”

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“…Genetic and biochemical analyses of the 31E8^E2C protein have demonstrated that the 31E8 domain is required for transcriptional repression. This is due to the recruitment of cellular corepressors, such as the histone deacetylase 3 (HDAC3)/N-CoR complex, by the 31E8 domain (1,31). The analysis of E8^E2C functions in the context of HPV16, the most potent cancer-inducing HPV, has revealed differences from HPV31.…”

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Growth Inhibition of HeLa Cells Is a Conserved Feature of High-Risk Human Papillomavirus E8^E2C Proteins and Can Also Be Achieved by an Artificial Repressor Protein

Fertey

Hurst

Straub

et al. 2011

J Virol

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Infections with certain human papillomaviruses (HPV), such as type 16 (HPV16), 18, or 31, are a necessary risk factor for the development of cervical cancer. Transcript analyses of several HPV revealed that the viral E2 gene encodes both the E2 regulator protein and the E8^E2C protein, which differ in their amino termini. Up to now, functional studies have focused on HPV31 E8^E2C and demonstrated that it is a potent repressor of viral transcription and replication. However, recent analyses of HPV16 genomes have suggested that E8^E2C proteins may differ in their activities. Therefore, we performed a comparative analysis of E8^E2C proteins of HPV16, -18, and -31. All E8^E2C proteins potently inhibited HPV E6/E7 oncogene promoters, and also displayed long-distance transcriptional-repression activities. Furthermore, the expression of all E8^E2C proteins inhibited the growth of HeLa cells. Expression of E8^E2C proteins rapidly increased the protein levels of the E6 and E7 targets p53 and p21, consistent with the repression of the endogenous HPV18 E6/E7 promoter. All E8^E2C proteins induced G 1 arrest more efficiently than E2 proteins and activated senescence markers. Furthermore, we demonstrate that the 31E8 domain can be functionally replaced by the KRAB repression domain derived from KOX1. The KRAB-E2C fusion protein possesses long-distance transcriptional-repression activity and inhibits the growth of HeLa cells comparably to E8^E2C. Taken together, our results suggest that the E8^E2C proteins of HPV16, -18, and -31 are highly conserved transcriptional repressors that inhibit the growth of HeLa cells by repression of E6/E7 transcription but do not have proapoptotic activities.Persistent infections with human papillomaviruses (HPV), such as HPV type 16 (HPV16), -18, or -31, are a necessary risk factor for the development of invasive cervical cancer (4, 42, 47). HPV16 accounts for ϳ55%, HPV18 for ϳ16%, and HPV31 for only ϳ4% of cervical cancers worldwide (3), but the underlying differences accounting for these behaviors are not well understood. The viral E2 gene expresses crucial regulatory proteins involved in replication, transcription, and maintenance of viral genomes (19,40). The E2 protein is a sequence-specific DNA binding protein that recognizes four E2 binding sites (E2BS) upstream of the HPV E6/E7 promoter through its C-terminal domain (E2C) (26). The amino-terminal domain of E2 (E2TA) is responsible for the activation of transcription, the activation of viral replication, and attachment to mitotic chromosomes (19,40). In addition to E2, several HPV express a spliced RNA that expresses a fusion protein consisting of the small E8 domain fused to E2C (9,29,33,36,37). The functions of the E8^E2C protein have been mainly investigated with HPV31. It was shown that E8^E2C knockout HPV31 genomes displayed a strong overreplication of viral genomes in short-term analyses (37). Despite this, in stable cell lines, HPV31 E8^E2C (31E8^E2C) knockout genomes were not maintained as episomes but only found integrated into t...

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Growth Inhibition of HeLa Cells Is a Conserved Feature of High-Risk Human Papillomavirus E8^E2C Proteins and Can Also Be Achieved by an Artificial Repressor Protein

Fertey

Hurst

Straub

et al. 2011

J Virol

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“…These MS data were then analyzed with CompPASS (Comparative Proteomic Analysis Software Suite), which relies on an unbiased comparative approach for identifying high-confidence candidate-interacting proteins (HCIPs) (85). This technology has been successfully used to identify protein interactors among the hundreds of proteins typically identified in immunoprecipitation-MS experiments (5,12,72,73,95).…”

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Identification and Proteomic Analysis of Distinct UBE3A/E6AP Protein Complexes

Martínez-Noël

Galligan

Sowa

et al. 2012

Molecular and Cellular Biology

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The E6AP ubiquitin ligase catalyzes the high-risk human papillomaviruses' E6-mediated ubiquitylation of p53, contributing to the neoplastic progression of cells infected by these viruses. Defects in the activity and the dosage of E6AP are linked to Angelman syndrome and to autism spectrum disorders, respectively, highlighting the need for precise control of the enzyme. With the exception of HERC2, which modulates the ubiquitin ligase activity of E6AP, little is known about the regulation or function of E6AP normally. Using a proteomic approach, we have identified and validated several new E6AP-interacting proteins, including HIF1AN, NEURL4, and mitogen-activated protein kinase 6 (MAPK6). E6AP exists as part of several different protein complexes, including the proteasome and an independent high-molecular-weight complex containing HERC2, NEURL4, and MAPK6. In examining the functional consequence of its interaction with the proteasome, we found that UBE3C (another proteasome-associated ubiquitin ligase), but not E6AP, contributes to proteasomal processivity in mammalian cells. We also found that E6 associates with the HERC2-containing high-molecular-weight complex through its binding to E6AP. These proteomic studies reveal a level of complexity for E6AP that has not been previously appreciated and identify a number of new cellular proteins through which E6AP may be regulated or functioning. E6AP was originally discovered as the cellular protein that mediates the binding of the E6 protein of the high-risk human papillomaviruses (HPVs) to the tumor suppressor p53 (35). Subsequently, E6AP was shown to catalyze the E6-dependent transfer of ubiquitin to p53, targeting it for degradation by the 26S proteasome. As such, E6AP was the first mammalian ubiquitin (Ub) ligase to be described (36,37,80).E6AP is a 100-kDa protein containing a conserved carboxyterminal domain spanning 350 amino acids, referred to as the HECT domain (homologous to E6AP carboxy terminus), that defines a family of E3 Ub ligases (34). This domain participates directly in the transfer of ubiquitin from an E2 ubiquitin-conjugating enzyme to a conserved cysteine residue through a thiolester bond (34). E6AP then directs the transfer of ubiquitin from this active-site cysteine to a lysine residue of an associated substrate. Replacement of the active-site cysteine with alanine renders E6AP unable to accept ubiquitin and therefore unable to catalyze the transfer of ubiquitin to the target protein. This C/A substitution mutant is inactive and functions in a dominant-negative (DN) manner (88). Three different isoforms of E6AP that are generated by differential splicing from the same gene have been described (98). These three isoforms differ in their amino-terminal sequences, and it is not yet known whether they differ in function or substrate specificity.The E6AP protein is encoded by the UBE3A gene located in an imprinted region on chromosome 15q11-q13. As a consequence of the imprinting, only the maternal UBE3A allele is expressed in certain areas of the br...

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“…The HPV31 E8/E2 protein represses transcription and extra-chromosomal replication; many interactions responsible for these repressive functions are described. [41][42][43] However, the HPV31 E8 and BPV1 E8 proteins belong to different E8 clades (Puustusmaa and Abroi, manuscript in preparation). In addition, the subcellular localization of HPV31 E8/E2 has not yet been studied.…”

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Characterization of the nuclear matrix targeting sequence (NMTS) of the BPV1 E8/E2 protein — the shortest known NMTS

Sankovski

Karro²,

Sepp

et al. 2015

Nucleus

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Technological advantages in sequencing and proteomics have revealed the remarkable diversity of alternative protein isoforms. Typically, the localization and functions of these isoforms are unknown and cannot be predicted. Also the localization signals leading to particular subnuclear compartments have not been identified and thus, predicting alternative functions due to alternative subnuclear localization is limited only to very few subnuclear compartments. Knowledge of the localization and function of alternative protein isoforms allows for a greater understanding of cellular complexity. In this article, we characterize a short and well-defined signal targeting the bovine papillomavirus type 1 E8/E2 protein to the nuclear matrix. The targeting signal comprises the peptide coded by E8 ORF, which is spliced together with part of the E2 ORF to generate the E8/E2 mRNA. Localization to the nuclear matrix correlates well with the transcription repression activities of E8/E2; a single point mutation directs the E8/E2 protein into the nucleoplasm, and transcription repression activity is lost. Our data prove that adding as few as~10 amino acids by alternative transcription/alternative splicing drastically alters the function and subnuclear localization of proteins. To our knowledge, E8 is the shortest known nuclear matrix targeting signal.

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NCoR1 Mediates Papillomavirus E8^E2C Transcriptional Repression

Cited by 39 publications

References 67 publications

Growth Inhibition of HeLa Cells Is a Conserved Feature of High-Risk Human Papillomavirus E8^E2C Proteins and Can Also Be Achieved by an Artificial Repressor Protein

Growth Inhibition of HeLa Cells Is a Conserved Feature of High-Risk Human Papillomavirus E8^E2C Proteins and Can Also Be Achieved by an Artificial Repressor Protein

Identification and Proteomic Analysis of Distinct UBE3A/E6AP Protein Complexes

Characterization of the nuclear matrix targeting sequence (NMTS) of the BPV1 E8/E2 protein — the shortest known NMTS

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