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Regulation of Human Papillomavirus Type 1 Replication by the Viral E2 Protein

Regulation of Human Papillomavirus Type 1 Replication by the Viral E2 Protein,10.1006/viro.2001.1037,Virology,Gerald Van Horn,Saifuddin Sheikh,Saleem

Regulation of Human Papillomavirus Type 1 Replication by the Viral E2 Protein   (Citations: 6)
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The E1 and E2 proteins encoded by papillomaviruses are required for viral replication. Earlier studies have shown that the viral E2 protein plays an important role in replication by targeting the E1 helicase to the origin of replication (ori). We have previously shown that the E1 protein of human papillomavirus (HPV) type 1 is sufficient for the in vivo replication of ori plasmids, although the E2 protein stimulates replication. In this study, we have further analyzed the role of the E2 protein in HPV-1 replication. The optimal ori of HPV-1 contains one putative E1 binding site (E1BS) and two putative E2 binding sites, E2BS-3 and E2BS-4. Plasmid pori171, containing the optimal ori, replicates to much higher levels than plasmid pori312, which includes an additional upstream E2 binding site, E2BS-2, located 75 nucleotides upstream of E2BS-3. To study the possible role of E2BS-2 and other upstream sequences in E2-dependent downregulation of replication, transient replication analysis was done in the presence of increasing levels of the E2 protein. Interestingly, inhibition of pori312 replication was more severe at higher levels of E2, suggesting that this protein may also negatively regulate HPV-1 replication. Deletion of sequences from pori312 containing an additional putative E2BS, E2BS-2A, relieved the repression of replication to a significant extent, while replacement of E2BS-2 with a different sequence of the same length had a modest effect. These results suggest that E2BS-2A plays a major and E2BS-2 a minor role in the negative regulation of HPV-1 replication at high E2 levels. Electrophoretic mobility-shift assays showed that the purified E2 protein bound with high affinity to E2BS-3 and weakly to the other putative E2BSs located within the viral long control region. EMSA using various ori fragments showed the formation of multiple E2–DNA complexes which likely represent binding of E2 to multiple E2BSs present within the HPV-1 ori. Our data are consistent with the assembly of ori–protein complexes at high E2 levels that are impaired for replication and further suggest that E2 may regulate HPV-1 replication by a mechanism involving interaction between the E2 protein bound to E2BSs at a distance.
Journal: Virology , vol. 287, no. 1, pp. 214-224, 2001
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    • ...Previous reports also showed that the absence of an E2 expression plasmid resulted in no replication or a significant loss of replication but that a higher ratio of E2 expression plasmid reduced the replication efficiency, with ratios ranging from 3:1 to 60:1 showing optimal replication (12, 24, 25, 27)...

    Takashi Minoet al. Inhibition of DNA Replication of Human Papillomavirus by Artificial Zi...

    • ...The E2 gene product plays various roles in HPV replication, being involved in E6 expression regulation and by indirectly controlling E1. The major role of the E2 protein in replication is to target E1, which is a weak DNA binding protein, to the ori (26)...
    • ...The replication of papillomaviruses requires both viral E1 and E2 proteins (26)...
    • ...The replication rate of HPV changes reciprocally, depending on the level of E2. Thus, the E1/E2 ratio is probably significant in this replication regulation (26)...

    Krzysztof Lukaszuket al. Human Papillomavirus Type 16 Status in Cervical Carcinoma Cell DNA Ass...

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