title: Activation of transcription and retrotransposition of a novel retroelement, Steamer, in neoplastic hemocytes of the mollusk Mya arenaria.
abstract: Bivalve mollusks of the North Atlantic, most prominently the soft shell clam Mya arenaria, are afflicted with an epidemic transmissible disease of the circulatory system closely resembling leukemia. The disease is characterized by a dramatic expansion of blast-like cells in the hemolymph with high mitotic index. Examination of hemolymph of diseased clams revealed high levels of reverse transcriptase activity, the hallmark of retroviruses and retroelements. By deep sequencing of RNAs from hemolymph, we identified transcripts of a novel retroelement, here named Steamer. The DNA of the element is marked by long terminal repeats and encodes a single large protein with similarity to mammalian retroviral Gag-Pol proteins. Steamer mRNA levels were specifically elevated in diseased hemocytes, and high expression was correlated with disease status. DNA copy number per genome was present at enormously high levels in diseased hemocytes, indicative of extensive reverse transcription and retrotransposition. Steamer activation in M. arenaria is an example of a catastrophic induction of genetic instability that may initiate or advance the course of leukemia.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032; Departamento de Ciencias Biologicas, Universidad Andres Bello, Viña del Mar 2520000, Chile;
authors.forename: Gloria
authors.initials: G
authors.lastname: Arriagada
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032;
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Metzger
authors.affiliation: Environment Canada, Water Science & Technology Directorate, Burlington, ON, Canada L7R 4A6; and.
authors.forename: Annette F
authors.initials: AF
authors.lastname: Muttray
authors.affiliation: Environment Canada, Water Science & Technology Directorate, Burlington, ON, Canada L7R 4A6; and.
authors.forename: James
authors.initials: J
authors.lastname: Sherry
authors.affiliation: Environment Canada, Water Science & Technology Directorate, Burlington, ON, Canada L7R 4A6; and.
authors.forename: Carol
authors.initials: C
authors.lastname: Reinisch
authors.affiliation: Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY 10032.
authors.forename: Craig
authors.initials: C
authors.lastname: Street
authors.affiliation: Center for Infection and Immunity, Mailman School of Public Health, Columbia University, New York, NY 10032.
authors.forename: W Ian
authors.initials: WI
authors.lastname: Lipkin
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032; spg1@columbia.edu.
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Goff
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D018628:Gene Dosage; D019337:Hematologic Neoplasms / Q000235:genetics; D006434:Hemocytes / Q000378:metabolism*; D006458:Hemolymph / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D049892:Mya / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D012313:RNA / Q000235:genetics; D018626:Retroelements / Q000235:genetics*; D015533:Transcriptional Activation
chemical_list: D018626:Retroelements; D012313:RNA; D004247:DNA
keywords: disseminated neoplasia; hemic neoplasia; integration; mobile genetic element; retrotransposon