Genomic cloning and restriction site mapping of a porcine adenovirus isolate: demonstration of genomic stability in porcine adenovirus

Crystallographic structure of porcine adenovirus type 4 fiber head and galectin domains

Adenovirus isolate NADC-1, a strain of porcine adenovirus type 4, has a fiber containing an N-terminal virus attachment region, shaft and head domains, and a C-terminal galectin domain connected to the head by an RGD-containing sequence. The crystal structure of the head domain is similar to previously solved adenovirus fiber head domains, but specific residues for binding the coxsackievirus and adenovirus receptor (CAR), CD46, or sialic acid are not conserved. The structure of the galectin domain reveals an interaction interface between its two carbohydrate recognition domains, locating both sugar binding sites face to face. Sequence evidence suggests other tandem-repeat galectins have the same arrangement. We show that the galectin domain binds carbohydrates containing lactose and N-acetyl-lactosamine units, and we present structures of the galectin domain with lactose, N-acetyl-lactosamine, 3-aminopropyl-lacto-N-neotetraose, and 2-aminoethyl-tri(N-acetyl-lactosamine), confirming the domain as a bona fide galectin domain.

Crystallization of the head and galectin-like domains of porcine adenovirus isolate NADC-1 fibre

The porcine adenovirus NADC-1 isolate, a strain of porcine adenovirus type 4, has a fibre with an atypical architecture. In addition to a classical virus attachment region, shaft and head domains, it contains an additional galectin like domain C-terminal to the head domain and connected to the head domain by a long RGD-containing loop. The galectin-like domain contains two putative carbohydrate-recognition domains. The head and galectin-like domains have been independently crystallized. Diffraction data have been obtained to 3.2 angstrom resolution from crystals of the head domain and to 1.9 angstrom resolution from galectin-like domain crystals.

Sequence analysis and deletion of porcine adenovirus serotype 5 E3 region

A 3000 basepair (bp) region corresponding to the E3 region, the flanking pVIII and part of the fiber protein genes, of the two prototype strains (HNF-61 and HNF-70) of porcine adenovirus serotype five (PAdV-5) was sequenced. A potential E3 promoter and poly-A signals were identified. The size of the E3 region was 2039 (strain HNF-61) and 2020 bp (strain HNF-70) the largest E3 so far reported among PAdVs. Three open reading frames (ORF2-4) were identified within the E3 region. Based on the predicted amino acid (aa) sequences ORF2 was similar to other adenovirus E3 ORFs, ORF3 showed some similarity to a bovine adenovirus (BAdV-1) ORF. ORF4 was unique to PAdV-5. E3 mRNA transcripts were detected early in infection by Northern blot analysis. Genomic clones of HNF-70 with a 1505 or 1237 bp deletions in the E3 region were constructed to map non-essential regions. After transfection of the DNA into swine testicle cells, virions were recovered for only the shorter 1237 bp deletion. At least 60% of the E3 region was not essential for virus replication, bringing the theoretical vector capacity of a helper independent PAdV-5 to 2.9 kb.

Porcine adenoviruses types 1, 2 and 3 have short and simple early E-3 regions

The nucleotide sequence of the E-3 region genes, the hexon associated protein pVIII genes, and part of the fiber genes coding for the N-terminal tail regions, of porcine adenovirus (PAV) types 1 and 2 were determined. The sizes of the E-3 regions were found to be 1162 and 1222 bp, respectively. The five open reading frames (ORF) encoded within the sequenced regions of PAV types 1 and 2 shared a high degree of homology with the published sequences of the corresponding ORFs of PAV-3. The E-3 regions of PAV types 1, 2 and 3 were further characterized by Northern blot analysis and 5' and 3' end mapping of the transcripts by S1 nuclease analysis. The results of these experiments indicated that the E-3 regions in these three viruses are shorter and simpler in organization than the E-3 regions of human adenoviruses. A potential promoter for the E-3 regions of these PAVs was identified.

Sequence analysis of the fiber genomic region of a porcine adenovirus predicts a novel fiber protein

The complete nucleotide sequence of the putative fiber protein of a porcine adenovirus isolate, NADC-1, was determined. The coding sequence for the fiber protein was found to be 2112 nucleotides, predicting a 703 amino acid protein with a calculated molecular mass of 76,681 Da. The coding sequence is located between 86 and 92.5 map units. A polyadenylation signal was found 44 bases downstream of the stop codon. Northern hybridization analysis identified a band at 2.4 kb, which likely includes the primary transcript plus a tripartite leader (typically found with adenovirus transcripts) and a polyA(+) tail. The predicted NADC-1 fiber protein was found to have a tail domain comparable in size and sequence to most adenovirus fiber proteins, a comparatively short shaft region, and a head region that was more than twice as large as that of other adenovirus fiber proteins. Each of the three structural domains (tail, shaft, and head) of the predicted NADC-1 fiber protein was found to be most similar to the corresponding domain of a different mammalian adenovirus. The NADC-1 fiber head contained an RGD sequence, a motif that is found in the penton protein of other adenoviruses. Furthermore, the predicted amino acid sequence of the C-terminal half of the NADC-1 fiber head has significant homology to S-lectin proteins, a characteristic not shared with other adenovirus fiber proteins. Thus the predicted amino acid sequence of the NADC-1 fiber head is unique among adenoviruses for which the sequence of the fiber protein is known.

Restriction endonuclease analysis and physical mapping of the genome of porcine adenovirus type 5

The HNF61 and HNF70 isolates of porcine adenovirus type 5 (PAV-5) were cultivated in PK-15 cells, and viral DNA was extracted from the infected cells by a modified Hirt procedure. The DNAs were digested by each of 9 restriction endonucleases, and fragments representing the entire genomes were cloned. Based on the sizes of the restriction enzyme fragments, the genome of each isolate was estimated to be 33.2 kb. Physical maps for the 9 restriction endonucleases were constructed. The physical maps of the two isolates were identical for 5 of the restriction endonucleases, but 4 enzymes revealed differences in restriction sites occurring mainly between map units 78 and 83, which may include the E3 region of the genome. There were no similarities between the physical maps of PAV-5 and those described for the other 4 serotypes of PAV.

Identification and sequence analysis of the E1 genomic region of a porcine adenovirus

The complete nucleotide sequence of the putative early transcriptional region 1 (E1) of the genome of NADC-1, a porcine adenovirus, was determined. The E1 region of NADC-1 was found to be 3658 bp and located between 0 and 11.2 map units. Twelve potential open reading frames (ORFs) and five polyadenylation signals were identified in the r strand. The nucleotide sequence and each predicted amino acid sequence were compared to sequences available on a number of databases by a BLAST search and comparison. A single region of nucleotide sequence similarity was identified with the sequence of human adenovirus 5. Only 2 of the 12 potential ORFs encode polypeptides that have homology to known adenovirus polypeptides. For these predicted proteins, similarities were found with a number of adenovirus proteins. The strongest homology was found to potential E1 products of bovine adenovirus 3.

Sequence analysis of putative pVIII, E3 and fibre regions of porcine adenovirus type 3

Sequence analysis of a region of the genome of porcine adenovirus type 3 from map unit 79.5 to map unit 92 was performed. Homology studies revealed genes coding for the hexon-associated protein pVIII on the left and for the fibre protein on the right of the sequenced region. By analogy with the genomic organization of other adenoviruses, the 1179 bp sequence between the pVIII and fibre open reading frames, extending from map unit 81.3 to map unit 84.7, was identified as the equivalent of the E3 region of human adenoviruses. The deduced amino acid sequence of one of the three open reading frames of the putative E3 region showed homology with the 13.3K E3 protein of canine adenovirus type 2. The primary structure of the putative fibre protein was similar to that described for human adenovirus types 2 and 5, with a 14 pseudorepeat motif in the shaft region of the fibre. A 742 bp tandem repeat starting in the middle of the fibre gene and extending beyond the termination codon of this gene was observed.

Molecular cloning and physical mapping of porcine adenovirus types 1 and 2

The 25R strain of porcine adenovirus type 1 (PAV-1) and the A47 strain of PAV-2 were propagated in ST cells, and DNA was extracted from the infected cells by a modified Hirt method. The DNA of each virus was digested by each of nine restriction endonucleases, and restriction enzyme fragments representing the entire genome were cloned. The genomic size of each virus was approximately 33 kb. Physical maps for the nine restriction endonucleases were constructed from the results of double digestion and Southern blot hybridization experiments, and oriented with respect to the PAV-3 genome. PAV-1 and PAV-2 were found to be related genetically to PAV-3, and there was a closer relationship between PAV-1 and PAV-3 than between PAV-1 and PAV-2 or between PAV-2 and PAV-3.