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Molecular and Cellular Biology, June 2003, p. 3825-3836, Vol. 23, No. 11
0270-7306/03/$08.00+0     DOI: 10.1128/MCB.23.11.3825-3836.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Transcription of Endogenous and Exogenous R2 Elements in the rRNA Gene Locus of Drosophila melanogaster

Danna G. Eickbush and Thomas H. Eickbush*

Department of Biology, University of Rochester, Rochester, New York 146270-0211

Received 2 December 2002/ Returned for modification 15 January 2003/ Accepted 13 March 2003

R2 retrotransposons insert into the rRNA-encoding units (rDNA units) that form the nucleoli of insects. We have utilized an R2 integration system in Drosophila melanogaster to study transcription of foreign sequences integrated into the R2 target site of the 28S rRNA genes. The exogenous sequences were cotranscribed at dramatically different levels which closely paralleled the level of transcription of the endogenous R1 and R2 elements. Transcription levels were inversely correlated with the number of uninserted rDNA units, variation in this number having been brought about by the R2 integration system itself. Females with as few as 20 uninserted rDNA units per X chromosome had expression levels of endogenous and exogenous insertion sequences that were 2 orders of magnitude higher than lines that contained over 80 uninserted rDNA units per chromosome. R2 insertions only 167 bp in length exhibited this range of transcriptional regulation. Analysis of transcript levels in males suggested R2 insertions on the Y chromosome are not down-regulated to the same extent as insertions on the X chromosome. These results suggest that transcription of the rDNA units can be tightly regulated, but this regulation gradually breaks down as the cell approaches the minimum number of uninserted genes needed for survival.

* Corresponding author. Mailing address: Department of Biology, Hutchison Hall, University of Rochester, Rochester, NY 14627. Phone: (585) 275-7247. Fax: (585) 275-2070. E-mail: eick{at}mail.rochester.edu.

Molecular and Cellular Biology, June 2003, p. 3825-3836, Vol. 23, No. 11
0022-538X/03/$08.00+0     DOI: 10.1128/MCB.23.11.3825-3836.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Eickbush, D. G., Ye, J., Zhang, X., Burke, W. D., Eickbush, T. H. (2008). Epigenetic Regulation of Retrotransposons within the Nucleolus of Drosophila. Mol. Cell. Biol. 28: 6452-6461 [Abstract] [Full Text]  
  • Zhang, X., Zhou, J., Eickbush, T. H. (2008). Rapid R2 Retrotransposition Leads to the Loss of Previously Inserted Copies via Large Deletions of the rDNA Locus. Mol Biol Evol 25: 229-237 [Abstract] [Full Text]  
  • Ye, J., Eickbush, T. H. (2006). Chromatin Structure and Transcription of the R1- and R2-Inserted rRNA Genes of Drosophila melanogaster. Mol. Cell. Biol. 26: 8781-8790 [Abstract] [Full Text]  
  • Averbeck, K. T., Eickbush, T. H. (2005). Monitoring the Mode and Tempo of Concerted Evolution in the Drosophila melanogaster rDNA Locus. Genetics 171: 1837-1846 [Abstract] [Full Text]  
  • Maggert, K. A., Golic, K. G. (2005). Highly Efficient Sex Chromosome Interchanges Produced By I-CreI Expression in Drosophila. Genetics 171: 1103-1114 [Abstract] [Full Text]  
  • Zhang, X., Eickbush, T. H. (2005). Characterization of Active R2 Retrotransposition in the rDNA Locus of Drosophila simulans. Genetics 170: 195-205 [Abstract] [Full Text]  
  • Perez-Gonzalez, C. E., Burke, W. D., Eickbush, T. H. (2003). R1 and R2 Retrotransposition and Deletion in the rDNA Loci on the X and Y Chromosomes of Drosophila melanogaster. Genetics 165: 675-685 [Abstract] [Full Text]  


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