A vaccinia virus gene that is expressed throughout the reproductive cycle was found to have two sets of RNA start sites approximately 55 nucleotides apart. The site nearest to the coding segment is used early in infection and the one further upstream is used after DNA replication. A series of 5' to 3' deletions were made in the promoter region, and the truncated DNA segments were then ligated to the coding portion of the procaryotic chloramphenicol acetyltransferase gene to measure expression. The effects of these mutations on chloramphenicol acetyltransferase synthesis were determined in a vaccinia virus helper-dependent transient expression system and by forming infectious vaccinia virus recombinants that contain the chimeric genes. Deletions extending up to 31 nucleotides before the late RNA start site had no effect on either early or late expression. Removal of an additional 15 nucleotides produced a dramatic decrease in late expression but had no effect on early expression. The latter was not diminished until the deletion was extended from 31 to 24 nucleotides before the early RNA start site. These results were confirmed by transcriptional analyses. We concluded that this vaccinia virus gene has two promoters and that the regulatory signals for each are located within 31 nucleotides of their sites of transcription.
An examination of Autographa californica nuclear polyhedrosis virus DNA revealed the presence of five interspersed regions, rich in EcoRI restriction sites, which shared homologous sequences. These homologous regions (hr), designated hr1 to hr5, occur at or near the following EcoRI firagment junctions: hr1 EcoRI-B-EcoRI-I (0.0 map units); hr2, EcoRI-A-EcoRI-J (19.8 map units); hr3, EcoRI-C-EcoRI-G (52.9 map units); hr4, EcoRI-Q-EcoRI-L (69.8 map units); and hr5, EcoRI-S-EcoRI-X (88.0 map units). Four of these regions were identified, by cross-blot hybridization of HindIII-restricted A. californica nuclear polyhedrosis virus DNA, to be within the HindIII-AIB,-F,-L, and-Q fragments. The location of these regions and the identification of a fifth homologous region were confirmed, and their characterization was facilitated, by using two plasmids with HindIII-L or-Q fragment insertions, which contained the homologous regions hr2 and hr5, respectively. The sizes of the homologous regions were about 800 base pairs for hr2, 500 base pairs for hr5, and less than 500 base pairs for hr1, hr3, and hr4. A set of small EcoRI fragments (EcoRI minifragments) which ranged in size from 225 to 73 base pairs were detected in A. californica nuclear polyhedrosis virus DNA and HindIII-L and-Q fragments by polyacrylamide gel analysis. Some of the minifragments in viral DNA were present in extramolar amounts and corresponded in size to some of the minifragments present in HindIII-L and-Q. Clones of some of the EcoRI minifragments were used as probes in hybridizations to digests of viral DNA and of HindIII-L and-Q. The hybridization data, obtained under various levels of stringency, suggested that there was a degree of mismatching between the sequences which were responsible for the homology.
We present a genomic map of infectious laryngotracheitis virus (ILT) and an 18,912 bp sequence containing the entire unique short region and a portion of the flanking short repeats. In determining the genomic map, an 856 bp region repeated as many as 13 times was identified within the short repeats. The unique short sequence contains nine potential open reading frames (ORFs). Six of these ORFs show homology to other known herpesvirus unique short genes. Using the herpes simplex virus nomenclature, these genes are the US2, protein kinase, and glycoproteins G, D, I, and E (ORF 1, 2, 4, 6, 7, and 8, respectively). Interestingly, an open reading frame with homology to HSV-1 UL47 (ORF 3) is found in the unique short. One very large open reading frame (ORF 5) is present and contains a threonine-rich, degenerate repeat sequence. This gene appears to be unique to ILT among sequenced herpesviruses. Two ORFs were identified within the short repeat (SR) region. SRORF 1 is homologous to a gene (SORF3) found in the unique short region in both MDV and HVT, and appears to be specific to avian herpesviruses. SRORF 2 has homology to HSV US10.
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