Gopalakrishnan V, Khan S A
Department of Molecular Genetics and Biochemistry, University of Pittsburgh School of Medicine, PA 15261.
Proc Natl Acad Sci U S A. 1994 Sep 27;91(20):9597-601. doi: 10.1073/pnas.91.20.9597.
Previous studies on transient replication of papillomaviruses have shown an absolute requirement for the viral E1 and E2 proteins in DNA replication. Here we demonstrate that for human papillomavirus type 1a (HPV-1a) DNA, the E1 protein alone is sufficient for in vivo replication of plasmids containing the viral origin of replication. Replication was origin-specific and required the presence of a DNA sequence containing a putative E1 binding site, but the E2 binding sites were dispensable. In the presence of the E1 protein, E2 stimulated replication of plasmids containing the E1 and E2 binding sites, but no stimulation was observed when the origin plasmids lacked E2 binding sites. Conversely, in the presence of E1 alone, the E2 binding sites did not affect replication. Plasmids containing the replication origins of HPV-6b, HPV-18, and bovine papillomavirus type 1 (BPV-1) also replicated efficiently in the presence of the HPV-1a E1 and E2 proteins. However, plasmids containing the origins of HPV-6b and HPV-18 failed to replicate in the presence of HPV-1a E1 alone, whereas a plasmid containing the BPV-1 origin replicated to lower levels than the HPV-1a origin-containing plasmid. These results suggest that replication from papillomaviral origins in the presence of E1 alone is presumably dependent on the strength of E1-origin interactions. Additionally, E1-dependent replication is stimulated by the E2 protein in the presence of E2 binding sites.
先前关于乳头瘤病毒瞬时复制的研究表明，DNA复制过程中绝对需要病毒E1和E2蛋白。在此我们证明，对于1a型人乳头瘤病毒（HPV-1a）DNA，单独的E1蛋白就足以使含有病毒复制起点的质粒在体内进行复制。复制具有起点特异性，需要存在包含假定E1结合位点的DNA序列，但E2结合位点是可有可无的。在有E1蛋白存在的情况下，E2可刺激含有E1和E2结合位点的质粒的复制，但当起点质粒缺乏E2结合位点时未观察到刺激作用。相反，仅在有E1存在时，E2结合位点不影响复制。含有HPV-6b、HPV-18和1型牛乳头瘤病毒（BPV-1）复制起点的质粒在有HPV-1a E1和E2蛋白存在时也能有效复制。然而，含有HPV-6b和HPV-18起点的质粒在仅存在HPV-1a E1时无法复制，而含有BPV-1起点的质粒复制水平低于含有HPV-1a起点的质粒。这些结果表明，仅在有E1存在时从乳头瘤病毒起点进行的复制大概取决于E1与起点相互作用的强度。此外，在有E2结合位点存在时，E2蛋白可刺激E1依赖性复制。
