An endogenous retrovirus presumed to have been endogenized or relocated recently in a marsupial, the red-necked wallaby

• Published in: Genome Vol. 65; no. 5; pp. 277 - 286
• Main Authors: Hayashi, Sakura, Shimizu, Konami, Honda, Yusuke, Katsura, Yukako, Koga, Akihiko
• Format: Journal Article
• Language: English
• Published: 1840 Woodward Drive, Suite 1, Ottawa, ON K2C 0P7 Canadian Science Publishing 01.05.2022; NRC Research Press; Canadian Science Publishing NRC Research Press
• Subjects: Albinism; albinisme; Amino Acid Sequence; Amino acids; Animals; Biosynthesis; Copy number variations; endogenous retrovirus; Endogenous retroviruses; Endogenous Retroviruses - genetics; Expressed sequence tags; Gag protein; Genetic aspects; Genomes; Host-virus relationships; Identification and classification; Infections; Insertion; long terminal repeat; longue répétition terminale; Macropodidae - genetics; marsupial; Melanin; Mutants; Open reading frames; Pigmentation; Polymerase chain reaction; Proviruses - genetics; Relocation; Retrotransposition; retrotransposon; rétrotransposon; rétrovirus endogène; Terminal Repeat Sequences; Tyrosinase; Virus research; Viruses; Japan; longue répétition terminale; albinisme; long terminal repeat; rétrotransposon; endogenous retrovirus; marsupial; rétrovirus endogène; retrotransposon; albinism
• ISSN: 0831-2796; 1480-3321
• DOI: 10.1139/gen-2021-0047

An albino infant wallaby was born to a mother with wild-type body color. PCR and sequencing analyses of TYR (encoding tyrosinase, which is essential for melanin biosynthesis) of this albino wallaby revealed a 7.1-kb-long DNA fragment inserted in the first exon. Since the fragment carried long terminal repeats, we assumed it to be a copy of an endogenous retrovirus, which we named walb. We cloned other walb copies residing in the genomes of this species and of another wallaby species. The copies exhibited length variation, and the longest copy (>8.0 kb) contained open reading frames whose deduced amino acid sequences were well aligned with those of gag, pol, and env of retroviruses. It is unknown through which of the following likely processes the walb copy was inserted into TYR: endogenization (infection of a germline cell by an exogenous virus), reinfection (infection by a virus produced from a previously endogenized provirus), or retrotransposition (intracellular relocation of a provirus). In any case, the insertion into TYR is considered to have been a recent event on an evolutionary timescale because albino mutant alleles generally do not persist for long because of their deleterious effects in wild circumstances.