Affiliation:
1. Department of Biological Sciences, University of Idaho, Moscow, Idaho
2. Department of Biological Sciences, Texas Tech University, Lubbock, Texas
Abstract
ABSTRACT
A large percentage of the repetitive elements in mammalian genomes are retroelements, which have been moved primarily by LINE-1 retrotransposons and endogenous retroviruses. Although LINE-1 elements have remained active throughout the mammalian radiation, specific groups of endogenous retroviruses generally remain active for comparatively shorter periods of time. Identification of an unusual extinction of LINE-1 activity in a group of South American rodents has opened a window for examination of the interplay in mammalian genomes between these ubiquitous retroelements. In the course of a search for any type of repetitive sequences whose copy numbers have substantially changed in
Oryzomys palustris
, a species that has lost LINE-1 activity, versus
Sigmodon hispidus
, a closely related species retaining LINE-1 activity, we have identified an endogenous retrovirus family differentially amplified in these two species. Analysis of three full-length, recently transposed copies, called mysTR elements, revealed
gag
,
pro
, and
pol
coding regions containing stop codons which may have accumulated either before or after retrotransposition. Isolation of related sequences in
S. hispidus
and the LINE-1 active outgroup species,
Peromyscus maniculatus
, by PCR of a
pro-pol
region has allowed determination of copy numbers in each species. Unusually high copy numbers of approximately 10,000 in
O. palustris
versus 1,000 in
S. hispidus
and 4,500 in the more distantly related
P.maniculatus
leave open the question of whether there is a connection between endogenous retrovirus activity and LINE-1 inactivity. Nevertheless, these independent expansions of mysTR represent recent amplifications of this endogenous retrovirus family to unprecedented levels.
Publisher
American Society for Microbiology
Subject
Virology,Insect Science,Immunology,Microbiology
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