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Mol. Cell. Biol., 01 1995, 19-25, Vol 15, No. 1
DH Kass, MA Batzer and PL Deininger
The Alu repetitive family of short interspersed elements (SINEs) in
primates can be subdivided into distinct subfamilies by specific diagnostic
nucleotide changes. The older subfamilies are generally very abundant,
while the younger subfamilies have fewer copies. Some of the youngest Alu
elements are absent in the orthologous loci of nonhuman primates,
indicative of recent retroposition events, the primary mode of SINE
evolution. PCR analysis of one young Alu subfamily (Sb2) member found in
the low-density lipoprotein receptor gene apparently revealed the presence
of this element in the green monkey, orangutan, gorilla, and chimpanzee
genomes, as well as the human genome. However, sequence analysis of these
genomes revealed a highly mutated, older, primate- specific Alu element was
present at this position in the nonhuman primates. Comparison of the
flanking DNA sequences upstream of this Alu insertion corresponded to
evolution expected for standard primate phylogeny, but comparison of the
Alu repeat sequences revealed that the human element departed from this
phylogeny. The change in the human sequence apparently occurred by a gene
conversion event only within the Alu element itself, converting it from one
of the oldest to one of the youngest Alu subfamilies. Although gene
conversions of Alu elements are clearly very rare, this finding shows that
such events can occur and contribute to specific cases of SINE subfamily
evolution.
Copyright © 1995, American Society for Microbiology
Gene conversion as a secondary mechanism of short interspersed element (SINE) evolution
Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, New Orleans 70112.
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