Document Detail

Concerted evolution of the tandemly repeated genes encoding primate U2 small nuclear RNA (the RNU2 locus) does not prevent rapid diversification of the (CT)n.(GA)n microsatellite embedded within the U2 repeat unit.
MedLine Citation:
PMID:  8825646     Owner:  NLM     Status:  MEDLINE    
The RNU2 locus encoding human U2 small nuclear RNA (snRNA) is organized as a nearly perfect tandem array containing 5 to 22 copies of a 5.8-kb repeat unit. Just downstream of the U2 snRNA gene in each 5.8-kb repeat unit lies a large (CT)n.(GA)n dinucleotide repeat (n approximately equal to 70). This form of genomic organization, in which one repeat is embedded within another, provides an unusual opportunity to study the balance of forces maintaining the homogeneity of both kinds of repeats. Using a combination of field inversion gel electrophoresis and polymerase chain reaction, we have been able to study the CT microsatellites within individual U2 tandem arrays. We find that the CT microsatellites within an RNU2 allele exhibit significant length polymorphism, despite the remarkable homogeneity of the surrounding U2 repeat units. Length polymorphism is due primarily to loss or gain of CT dinucleotide repeats, but other types of deletions, insertions, and substitutions are also frequent. Polymorphism is greatly reduced in regions where pure (CT)n tracts are interrupted by occasional G residues, suggesting that irregularities stabilize both the length and the sequence of the dinucleotide repeat. We further show that the RNU2 loci of other catarrhine primates (gorilla, chimpanzee, orangutan, and baboon) contain orthologous CT microsatellites; these also exhibit length polymorphism, but are highly divergent from each other. Thus, although the CT microsatellite is evolving far more rapidly than the rest of the U2 repeat unit, it has persisted through multiple speciation events spanning > 35 Myr. The persistence of the CT microsatellite, despite polymorphism and rapid evolution, suggests that it might play a functional role in concerted evolution of the RNU2 loci, perhaps as an initiation site for recombination and/or gene conversion.
D Liao; A M Weiner
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Genomics     Volume:  30     ISSN:  0888-7543     ISO Abbreviation:  Genomics     Publication Date:  1995 Dec 
Date Detail:
Created Date:  1997-02-06     Completed Date:  1997-02-06     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  8800135     Medline TA:  Genomics     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  583-93     Citation Subset:  IM    
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520-8024, USA.
Data Bank Information
Bank Name/Acc. No.:
GENBANK/U36505;  U36506;  U36507;  U36508;  U36509;  U36510;  U36511;  U36512;  U36513;  U36514;  U36515;  U36516;  U36517;  U36518;  U36519;  U36520;  U36521;  U36522;  U36523;  U36524;  U36525;  U36526;  U36527;  U36528;  U36529;  U36530;  U36531;  U36532;  U36533;  U36534
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MeSH Terms
Base Sequence
DNA / genetics
Dinucleotide Repeats / genetics*
Molecular Sequence Data
Polymerase Chain Reaction
Polymorphism, Genetic
RNA, Small Nuclear / genetics*
Repetitive Sequences, Nucleic Acid / genetics
Sequence Homology, Nucleic Acid
Grant Support
Reg. No./Substance:
0/RNA, Small Nuclear; 9007-49-2/DNA

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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