Open AccessEpigenetic Regulation of Retrotransposons within the Nucleolus of Drosophila
Author(s) -
Danna G. Eickbush,
Junqiang Ye,
Xian Zhang,
William D. Burke,
Thomas H. Eickbush
Publication year - 2008
Publication title -
molecular and cellular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.14
H-Index - 327
eISSN - 1067-8824
pISSN - 0270-7306
DOI - 10.1128/mcb.01015-08
Subject(s) - biology , retrotransposon , genetics , locus (genetics) , nucleolus , transposable element , gene , ribosomal dna , transcription (linguistics) , ribosomal rna , genome , phylogenetics , cytoplasm , linguistics , philosophy
R2 retrotransposable elements exclusively insert into a conserved region of the tandemly organized 28S rRNA genes. Despite inactivating a subset of these genes, R2 elements have persisted in the ribosomal DNA (rDNA) loci of insects for hundreds of millions of years. Controlling R2 proliferation was addressed in this study using lines ofDrosophila simulans previously shown to have either active or inactive R2 retrotransposition. Lines with active retrotransposition were shown to have high R2 transcript levels, which nuclear run-on transcription experiments revealed were due to increased transcription of R2-inserted genes. Crosses between R2 active and inactive lines indicated that an important component of this transcriptional control is linked to or near the rDNA locus, with the R2 transcription level of the inactive parent being dominant. Pulsed-field gel analysis suggested that the R2 active and inactive states were determined by R2 distribution within the locus. Molecular and cytological analyses further suggested that the entire rDNA locus from the active line can be silenced in favor of the locus from the inactive line. This silencing of entire rDNA loci represents an example of the large-scale epigenetic control of transposable elements and shares features with the nucleolar dominance frequently seen in interspecies hybrids.