Sequence and structure of the extrachromosomal palindrome encoding the ribosomal RNA genes in Dictyostelium.

TitleSequence and structure of the extrachromosomal palindrome encoding the ribosomal RNA genes in Dictyostelium.
Publication TypeJournal Article
Year of Publication2003
AuthorsSucgang, R, Chen, G, Liu, W, Lindsay, R, Lu, J, Muzny, DM, Shaulsky, G, Loomis, W, Gibbs, R, Kuspa, A
JournalNucleic Acids Res
Volume31
Issue9
Pagination2361-8
Date Published2003 May 01
ISSN1362-4962
KeywordsAnimals, Chromosome Mapping, Dictyostelium, DNA, Protozoan, In Situ Hybridization, Fluorescence, Molecular Sequence Data, Plasmids, RNA, Ribosomal, Sequence Analysis, DNA
Abstract

Ribosomal RNAs (rRNAs) are encoded by multicopy families of identical genes. In Dictyostelium and other protists, the rDNA is carried on extrachromosomal palindromic elements that comprise up to 20% of the nuclear DNA. We present the sequence of the 88 kb Dictyostelium rDNA element, noting that the rRNA genes are likely to be the only transcribed regions. By interrogating a library of ordered YAC clones, we provide evidence for a chromosomal copy of the rDNA on chromosome 4. This locus may provide master copies for the stable transmission of the extrachromosomal elements. The extrachromosomal elements were also found to form chromosome-sized clusters of DNA within nuclei of nocodazole-treated cells arrested in mitosis. These clusters resemble true chromosomes and may allow the efficient segregation of the rDNA during mitosis. These rDNA clusters may also explain the cytological observations of a seventh chromosome in this organism.

Alternate JournalNucleic Acids Res.
PubMed ID12711681
PubMed Central IDPMC154234
Grant ListR01 HD035925 / HD / NICHD NIH HHS / United States
R01 HD35925 / HD / NICHD NIH HHS / United States