Regular articleComplete sequence of the 45-kb mouse ribosomal DNA repeat: analysis of the intergenic spacer☆☆
Section snippets
Sequencing of the intergenic spacer and assembly of a complete rDNA repeating unit
We identified a BAC clone (RP23-225M6) that contained one complete rDNA unit and subcloned and sequenced a substantial part of it (see Materials and methods). Sequences from the EcoRI site in the 28S rRNA gene to the SalI site downstream of the spacer promoter were deposited with DDBJ/EMBL/GenBank (31,129 bp; Accession No. AF441733).
The sequences of the enhancer and the 45S pre-rRNA gene are known, which allowed us to assemble one complete mouse rDNA repeating unit (45,309 bp) by combining the
Identification of the RPCI23 library BAC clone
In the database Genome Survey Sequences (dbGSS) we identified a BAC clone that contained rDNA sequences starting and finishing at the same EcoRI site in the 18S rRNA gene (Accession No. AZ700886—the SP6 end; Accession No. AZ700888—the T7 end). The identified clone (RP23-225M6) was from a library of partially EcoRI-digested female C57BL/6J genomic DNA and was obtained through the Internet (http://www.chori.org/bacpac). The clone DNA was Qiagen purified, digested with restriction enzymes,
Acknowledgements
We thank Ingrid Grummt (German Cancer Research Center, Heidelberg, Germany), Barbara Sollner-Webb (The Johns Hopkins University School of Medicine, Baltimore, MD, USA), and Milko Kermekchiev (Washington University, St. Louis, MO, USA) for mouse rDNA clones pSalA 1.0 and pSalA 1.2, p5′-1800, and pMr100, respectively. We thank Bojana Dimitrova (Institute of Molecular Biology, Sofia, Bulgaria) for her excellent technical assistance.
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