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[摘要]：The genome of varicella-zoster virus (VZV), a human alphaherpesvirus, consists of two unique regions, unique long (U-L) and unique short (U-S), each of which is flanked by inverted repeats. During replication, four isomers of the viral DNA are generated which are distinguished by the relative orientations of U-L and U-S. VZV virions predominantly package two isomeric forms of the genome that have a fixed orientation of U-L. An open reading frame (ORF) of unknown function, ORFS/L, also referred to as ORF0, is located at the extreme terminus of U-L, directly adjacent to the a-like sequences, which are known to be involved in cleavage and packaging of viral DNA. We demonstrate here that the ORFS/L protein localizes to the Golgi network in infected and transfected cells. Furthermore, we were able to demonstrate that deletion of the predicted ORFS/L gene is lethal, while retention of the N-terminal 28 amino acid residues resulted in viable yet replication-impaired virus. The growth defect was only partially attributable to the expression of the ORFS/L product, suggesting that the 5' region of ORFS/L contains a sequence element crucial for cleavage/packaging of viral DNA. Consequently, mutations introduced into the extreme 5' terminus of ORFS/L resulted in a defect in DNA cleavage, indicating that the region is indeed involved in the processing of viral DNA. Since the sequence element has no counterpart at the other end of U-L, we concluded that our results can provide an explanation for the almost exclusive orientation of the U-L seen in packaged VZV DNA. |
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