ABSTRACT INTRODUCTION REFERENCES MATERIALS & METHODS RESULTS & DISCUSSION Hong-Seok Ha 1, Jae-Won Huh 1, Dae-Soo Kim 2, Yun-Ji Kim 1, Ja-Rang Lee 1, Kung Ahn 1, Byung-Wook Cho 3, and Heui-Soo Kim 1,2 1 Division of Biological Sciences, College of Natural Sciences, Pusan National University, Busan , Republic of Korea 2 PBBRC, Interdisciplinary Research Program of Bioinformatics, College of Natural Sciences, Pusan National University, Busan , Republic of Korea 3 Department of Animal Science, College of Life Sciences, Pusan National University, Miryang , Republic of Korea 1.Altschul SF, Madden TL, Schaffer AA, Zhang J, Zhang W, Miller W, Lipman DJ (1997) Gapped Blast and PSI-BLAST: a new generation of protein database search program. Nucleic Acids Res 25: Akiyoshi DE, Denaro M, Zhu S, Greenstein JL, Banerjee P, Fishman JA (1998) Identification of a full- length cDNA for an endogenous retrovirus of miniature swine. J Virol 72: Denner J, Specke V, Thiesen U, Karlas A, Kurth R (2003) Genetic alteration of the long terminal repeat of an ecotropic porcine endogenous retrovirus during passage in human cells. Virology 314: Porcine endogenous retroviruses (PERVs) represent a potential infectious risk in the pig-to-human transplantation. Solitary long terminal repeat (LTR) elements of the PERV specifically affect the replication properties of single viruses and adjacent genes. Using PCR, sequencing, and bioinformatic approach, 12 members of solitary PERV LTR elements in various loci were identified and analyzed in various Korean pigs. The promoter activity of solitary LTR elements belonging to the PERV-A and –B families in Korean pigs using a luciferase assay were examined. Potential negative and positive factors for the PERV transcription regulation are identified from the deletion mutant analysis. The solitary PERV LTR element recently integrated into the haploid genome showed less promoter activity than the older in diploid genome of pigs. Methylation analyses of those solitary LTR elements indicated that the ‘young’ solitary LTR element was hypomethylated, whereas the ‘old’ solitary LTR elements were hypermethylated in most tissues examined. Our data suggest that the LTR elements having high promoter activity are hypermethylated to protect their biological activity in various tissues of pigs. Identification and characterization of PERV LTR elements in various Korean pig genomes 1. Pig transplant donor with infectious endogenous provirus (PERV) 2. “Donation” of organ to human recopient 3. Production of PERV, infection of nearby host cells 4. Systemic spread Adaptiation of virus to human host 5. Induction of disease 6. Epidemic spread GAGPOL ENV GAGPOL ENV Identification and characterization of PERV LTR elements in various Korean pig genomes Cell culture and transient transfection assay Molecular cloning and sequencing of PERV LTR elements Methylation analysis 5’-GCGC-3’ 3’-CGCG-5’ HhaI X 30 Denature Anneal Extension Template DNA 94 ℃ Primer DNA polymerase 55 ℃ 72 ℃ methylation