scholarly journals Transcription-modulatory activities of differentially spliced cDNAs encoding the E2 protein of human papillomavirus type 16

1999 ◽  
Vol 80 (9) ◽  
pp. 2461-2470 ◽  
Author(s):  
Nathalie Alloul ◽  
Levana Sherman
Keyword(s):  
Human Papillomavirus ◽  
Regulatory Protein ◽  
Protein Translation ◽  
Long Control Region ◽  
Dependent Manner ◽  
E2 Protein ◽  
Reading Frame ◽  
Human Papillomavirus Type 16 ◽  
C33a Cell ◽  
Alternatively Spliced

Human papillomavirus (HPV) type 16 expresses a variety of alternatively spliced polycistronic mRNAs encoding the E2 transcription-regulatory protein. These mRNAs initiate at the p97 promoter and contain the 880/2708 (a-type), 880/2581 (a′-type) and 226/2708 (d-type) splice sites upstream from the E2 open reading frame (ORF). Recent studies investigating the translational capacities of partial cDNAs representing three of these mRNAs indicated their abilities to function in E2 protein translation, although at different efficiencies. In the present study, the transcription-regulatory activities of the E2 cDNAs towards the virus long control region (LCR) have been examined. LCR regulation was evaluated in transient transfection assays by using the chloramphenicol acetyltransferase reporter gene linked to the HPV-16 LCR. Transfections were carried out into fibroblast (Cf2Th) and epithelial (C33A) cell lines. It is shown that all three E2 cDNAs transrepressed the virus LCR in a dose-dependent manner. Transrepression was mainly dependent on the function of the E2 ORF and was abolished or markedly reduced by premature termination or truncation of the E2 ORF. Transrepression activities exhibited by the various E2 cDNAs correlated with the previously defined efficiencies of E2 protein translation from the respective templates. The truncated E2 cDNAs exhibited variable low regulatory activities that correlated with the activities of the 5′ ORFs contained in each cDNA. The E6I and E1C ORFs transactivated the virus LCR whereas the E6IV cDNA transrepressed LCR activity. Thus, the 5′ ORFs contribute in different manners to the overall activities of the polycistronic cDNAs.

scholarly journals The Large and Small Isoforms of Human Papillomavirus Type 16 E6 Bind to and Differentially Affect Procaspase 8 Stability and Activity

2007 ◽  
Vol 81 (8) ◽  
pp. 4116-4129 ◽  
Author(s):  
Maria Filippova ◽  
Melyssa M. Johnson ◽  
Marnelli Bautista ◽  
Valery Filippov ◽  
Nadja Fodor ◽  
...  
Keyword(s):  
Human Papillomavirus ◽  
Cellular Response ◽  
Cellular Level ◽  
Dependent Manner ◽  
Death Domain ◽  
Hpv 16 ◽  
Human Papillomavirus Type 16 ◽  
E6 Oncoprotein ◽  
Alternatively Spliced ◽  
Interfering Rna

ABSTRACT Human papillomavirus type 16 (HPV-16) has developed numerous ways to modulate host-initiated immune mechanisms. The HPV-16 E6 oncoprotein, for example, can modulate the cellular level, and consequently the activity, of procaspase 8, thus modifying the cellular response to cytokines of the tumor necrosis factor family. E6 from HPV-16, but not E6 from the low-risk types 6b and 11, alters the cellular level of procaspase 8 in a dose-dependent manner. Both the large and small (E6*) isoforms of E6, which originate by way of alternate splicing, can modulate procaspase 8 stability. Intriguingly, although both isoforms bind to procaspase 8, the large isoform accelerates the degradation of procaspase 8 while the small isoform stabilizes it. Binding leads to a change in the ability of procaspase 8 to bind either to itself or to FADD (Fas-associated death domain), with the large version of E6 able to inhibit this binding while the small isoform does not. Consistent with this model, knockdown of the large version of E6 by small interfering RNA leads to increases in the levels of procaspase 8 and its binding to both itself and FADD. Thus, these alternatively spliced isoforms can modulate both the level and the activity of procaspase 8 in opposite directions.

scholarly journals NCoR1 Mediates Papillomavirus E8^E2C Transcriptional Repression

2010 ◽  
Vol 84 (9) ◽  
pp. 4451-4460 ◽  
Author(s):  
Maria L. C. Powell ◽  
Jennifer A. Smith ◽  
Mathew E. Sowa ◽  
J. Wade Harper ◽  
Thomas Iftner ◽  
...  
Keyword(s):  
Transcriptional Repression ◽  
Human Papillomaviruses ◽  
Full Length ◽  
Open Reading Frame ◽  
Long Control Region ◽  
E2 Protein ◽  
Reading Frame ◽  
Alternatively Spliced ◽  
E6 And E7 ◽  
Sirna Knockdown

ABSTRACT The papillomavirus E2 open reading frame encodes the full-length E2 protein as well as an alternatively spliced product called E8^E2C. E8^E2C has been best studied for the high-risk human papillomaviruses, where it has been shown to regulate viral genome levels and, like the full-length E2 protein, to repress transcription from the viral promoter that directs the expression of the viral E6 and E7 oncogenes. The repression function of E8^E2C is dependent on the 12-amino-acid N-terminal sequence from the E8 open reading frame (ORF). In order to understand the mechanism by which E8^E2C mediates transcriptional repression, we performed an unbiased proteomic analysis from which we identified six h igh-confidence c andidate i nteracting p roteins (HCIPs) for E8^E2C; the top two are NCoR1 and TBLR1. We established an interaction of E8^E2C with an NCoR1/HDAC3 complex and demonstrated that this interaction requires the wild-type E8 open reading frame. Small interfering RNA (siRNA) knockdown studies demonstrated the involvement of NCoR1/HDAC3 in the E8^E2C-dependent repression of the viral long control region (LCR) promoter. Additional genetic work confirmed that the papillomavirus E2 and E8^E2C proteins repress transcription through distinct mechanisms.

scholarly journals DNA Binding and Bending by the Human Papillomavirus Type 16 E2 Protein

1997 ◽  
Vol 272 (13) ◽  
pp. 8236-8242 ◽  
Author(s):  
Alison Thain ◽  
Kenneth Webster ◽  
Dave Emery ◽  
Anthony R. Clarke ◽  
Kevin Gaston
Keyword(s):  
Human Papillomavirus ◽  
Dna Binding ◽  
E2 Protein ◽  
Human Papillomavirus Type 16 ◽  
Dna Binding And Bending

scholarly journals Adeno-Associated Virus Major Rep78 Protein Disrupts Binding of TATA-Binding Protein to the p97 Promoter of Human Papillomavirus Type 16

2000 ◽  
Vol 74 (5) ◽  
pp. 2459-2465 ◽  
Author(s):  
Pei-Fen Su ◽  
Shu-Yuan Chiang ◽  
Cheng-Wen Wu ◽  
Felicia Y.-H. Wu
Keyword(s):  
Human Papillomavirus ◽  
Binding Protein ◽  
Core Promoter ◽  
Tata Binding Protein ◽  
Tata Box ◽  
Dependent Manner ◽  
Hpv 16 ◽  
Adeno Associated Virus ◽  
Human Papillomavirus Type 16 ◽  
E6 And E7

ABSTRACT Adeno-associated virus type 2 (AAV) is known to inhibit the promoter activities of several oncogenes and viral genes, including the human papillomavirus type 16 (HPV-16) E6 and E7 transforming genes. However, the target elements of AAV on the long control region (LCR) upstream of E6 and E7 oncogenes are elusive. A chloramphenicol acetyltransferase assay was performed to study the effect of AAV on the transcription activity of the HPV-16 LCR in SiHa (HPV-positive) and C-33A (HPV-negative) cells. The results reveal that (i) AAV inhibited HPV-16 LCR activity in a dose-dependent manner, (ii) AAV-mediated inhibition did not require the HPV gene products, and (iii) the AAV replication gene product Rep78 was involved in the inhibition. Deletion mutation analyses of the HPV-16 LCR showed that regulatory elements outside the core promoter region of the LCR may not be direct targets of AAV-mediated inhibition. Further study with the electrophoretic mobility shift assay demonstrated that Rep78 interfered with the binding of TATA-binding protein (TBP) to the TATA box of the p97 core promoter more significantly than it disrupted the preformed TBP-TATA complex. These data thus suggest that Rep78 may inhibit transcription initiation of the HPV-16 LCR by disrupting the interaction between TBP and the TATA box of the p97 core promoter.

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