Microsatellite spreading in the human genome: evolutionary mechanisms and structural implications.
Microsatellites are tandem repeat sequences abundant in the genomes of higher eukaryotes and hitherto considered as "junk DNA." Analysis of a human genome representative data base (2.84 Mb) reveals a distinct juxtaposition of A-rich microsatellites and retroposons and suggests their coevolution. The analysis implies that most microsatellites were generated by a 3'-extension of retrotranscripts, similar to mRNA polyadenylylation, and that they serve in turn as "retroposition navigators," directing the retroposons via homology-driven integration into defined sites. Thus, they became instrumental in the preservation and extension of primordial genomic patterns. A role is assigned to these reiterating A-rich loci in the higher-order organization of the chromatin. The disease-associated triplet repeats are mostly found in coding regions and do not show an association with retroposons, constituting a unique set within the family of microsatellite sequences.
Nadir
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E
Department of Molecular Genetics, Hebrew University, Hadassah Medical School, Jerusalem, Israel.
Margalit
H
H
Gallily
T
T
Ben-Sasson
S A
SA
D005075:Biological Evolution; D004276:DNA, Satellite; D006801:Humans; D018895:Microsatellite Repeats; D018626:Retroelements; D012689:Sequence Homology, Nucleic Acid
D004276:DNA, Satellite; D018626:Retroelements