Analysis of a ribosomal DNA intergenic spacer region from the yellow fever mosquito, Aedes aegypti

C. C.N. Wu, Ann M Fallon

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

We have sequenced the 1.8 kb intergenic spacer (IGS) region from an Aedes aegypti ribosomal DNA repeat and have identified conserved functional motifs shared with the related mosquito, Aedes albopictus. Despite the shorter length and greater homogeneity of the Ae. aegypti IGS region, the sequences of two potential RNA polymerase I core promoters and closely associated terminator elements were highly conserved. Primer extension analysis indicated that the predominant transcription initiation site in the Ae. aegypti rDNA repeat unit region lay at or near the A residue at nucleotide position 1003 in the 'upstream' RNA polymerase I promoter. This observation was supported by the higher sequence identity between the upstream promoters in Ae. aegypti and Ae. albopictus, relative to the downstream promoters. In contrast to strong similarities among proximal regulatory elements, the Ae. aegypti IGS sequence upstream of the transcription initiation site lacked the ordered array of contiguous ~ 200 nucleotide subrepeats previously found in the IGS of Ae. albopictus. in Ae. aegypti, only 4~50 nucleotide R subrepeats separated by unique sequences, followed by 2~50 nucleotide E subrepeats, occurred upstream of the transcription initiation site. Despite their differences in size and sequence, however, the four Ae. aegypti R subrepeats shared an internal structural organization that included a conserved core with 'spacer' promoters and recombinogenic elements similar to those in the longer Ae. albopictus subrepeats. These observations provide an important basis for further characterization of transcription specificity among mosquito RNA polymerase I promoters and associated regulatory elements, and contribute towards the eventual use of these elements in transgenic application.

Original languageEnglish (US)
Pages (from-to)19-29
Number of pages11
JournalInsect molecular biology
Volume7
Issue number1
DOIs
StatePublished - Feb 1998

Keywords

  • External transcribed spacer
  • Promoter
  • RNA polymerase I
  • Repeat unit
  • Ribosome

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