Sequencing and characterization of the potentially pathogenic genes of green turtle herpesvirus

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2003-12
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Nigro, Olivia De Santis
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Lu, Yuanan
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Microbiology (Marine Biology)
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University of Hawaii at Manoa
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Green turtle fibropapilloma (GTFP) is a debilitating and frequently fatal disease of green sea turtles. The etiological agent that causes this disease is unknown, however, recent evidence suggests that a novel green turtle herpesvirus (GTHV) is closely associated with GTFP. Because this virus has not been isolated or propagated in vitro cell culture to date, it is necessary to obtain more genomic information of GTHV in order to establish its pathogenic role in relation to GTFP. Using a modified genomic walking technique, based on inverse polymerase chain reaction (IPCR), a total of 9,032 base pair DNA sequences of the newfound GTHV was sequenced from tumor tissues of green turtles with fibropapillomas. This newly identified DNA fragment contains three potential pathogenic genes from the unique long (UL) region of GTHV: UL29 (DNA binding protein gene), UL28 (assembly protein gene) and UL27 (glycoprotein B gene). The UL29 gene was sequenced through 4 consecutive genomic walks in which a total viral fragment of 4,054 bp of sequence data was obtained. This viral DNA fragment contains the entire open reading frame of the UL29 gene (ORF), which is oriented in the 3' to 5' direction, and encodes the full-length genomic sequence of the DNA binding protein (DBP) gene (3,585 bp) corresponding to a protein of 1,195 amino acid residues. The viral fragment also encodes a partial sequence of the UL28 gene, which is oriented in the 3' to 5' direction as well. Through 2 subsequent genomic walks, the remainder of the UL28 was sequenced in its entirety, as well as a partial ORF of the UL27 gene. The UL28 gene has an ORF of 2,250 bp with a putative amino acid translation of 750 amino acids. Through 1 subsequent genomic walk the entire ORF of the UL27 gene was sequenced. This ORF is 2,551 bp long and overlaps the UL28 genome by 1 bp. The UL27 gene is oriented in the 3' to 5' direction and encodes the putative glycoprotein B (gB) transmembrane peptide, which is 851 amino acids in length. Phylogenetic analysis of GTHV DBP, UL28, and gB genes substantiated that this novel Chelonian herpesvirus is closely related to the Alphaherpesvirinae subfamily. Examination of the translated amino acid sequence further supports this categorization since GTHV DBP comprises a highly conserved zinc finger motif (CXLCX4RX2C) and a putative DNA binding domain, and exhibits high sequence homology to other alphaherpesviruses. The gB peptide also showed high homology to alphaherpesviruses in the extraviral, transmembrane and Cterminal tail regions of the peptide. Cloning and sequencing the genome of this putative herpesvirus will facilitate current understanding of its role in causing GTFP and the development of molecular- and immuno-based methods for the diagnosis and prevention of this devastating disease of green sea turtles.
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ix, 85 leaves
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Microbiology (Marine Biology); no. 3839
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