Sequence similarity between Borna disease virus p40 and a duplicated domain within the paramyxovirus and rhabdovirus polymerase proteins.

We report the sequence of a Borna disease virus clone (pBDV-40) that encodes a 40-kDa protein (p40) found in the nuclei of infected cells. Comparative sequence analysis indicates that p40 is distantly similar to two different regions in the L-polymerase proteins encoded by paramyxoviruses and rhabdoviruses. The p40 sequence similarity indicates a previously undetected duplication in these viral polymerases. Phylogenetic reconstruction suggests that the gene that encodes p40 last shared a common ancestor with these viral polymerase genes prior to the duplication event. These findings support the hypothesis that Borna disease virus is a negative-strand RNA virus and suggest that p40 is involved in transcription and/or replication. The discovery of a duplication within the polymerase proteins of paramyxoviruses and rhabdoviruses has profound implications for the mapping of enzymatic activities within these multifunctional proteins.

The herpes simplex virus immediate early protein ICP27 encodes a potential metal binding domain and binds zinc in vitro.

The herpes simplex virus type 1 (HSV-1) immediate-early regulatory proteins ICP27 and ICP0 each encode putative zinc-finger metal-binding domains. We utilized the technique of metal chelate affinity chromatography to demonstrate that ICP27 and ICP0 were able to bind to zinc in vitro. This property was further exploited to purify ICP27 from extracts of HSV-1-infected cells. The purification procedure also revealed that ICP27 possessed single-stranded DNA-binding activity. Analysis of ICP27 truncated peptides produced by in vitro translation verified that the zinc-binding region of ICP27 resides in the carboxy terminal 105 amino acids spanning the putative metal binding motif. However, a specific configuration of cysteine and histidine residues in this region was not required for binding to occur as demonstrated by the ability of a frame-shift mutation to bind with an efficiency similar to wild type. The mutated peptide retained four histidine and cysteine residues but in a configuration different from the consensus proposed for zinc-finger motifs. Therefore, while the region spanning the metal binding domain of ICP27 is essential for both the activator and repressor functions, and ICP27 binds zinc in vitro, it is not clear whether zinc binding in vivo is necessary for function.