Coding region deletions associated with the major form of rDNA interruption in Drosophila.

AUTOR(ES)

Rae, P M

RESUMO

The nucleotide sequences at and around the termini of 5 kb type 1 interruptions in three separate clones of D. melanogaster rDNA repeats have been determined, and have been compared with the sequence of the corresponding region of an insertion-free rDNA repeat. All three interrupted rDNA repeats contain a small deletion of 28S rRNA coding material at the left coding/insertion sequence junction. A second deletion was found in one of the three clones, ad other aberrations were suggested by the results of restriction enzyme digestions of unfractionated rDNA. The termini of 5 kb type 1 rDNA insertions in D. melanogaster were also compared with the corresponding regions of 28S rDNA interruptions in D. virilis: the insertion site is identical in the two species, but the termini of the two species' interruptions show no homology. I sequenced a 1.1 kb region of the 5 kb type 1 D. melanogaster rDNA interruption that covers the sequences of the 1 kb and 0.5 kb insertions. There is 98% homology between the rightmost 1 kb of the 5 kb interruption and the sequences of the shorter insertions. Data suggest that Drosophila rDNA interruptions arose as a transposable element, and that divergence had included length alterations generated by unequal crossing over.

Documentos Relacionados

• In vivo transcription of rDNA spacers in Drosophila.
• Duplicated rDNA sequences of variable lengths flanking the short type I insertions in the rDNA of Drosophila melanogaster.
• Absence of cytosine methylation at C-C-G-G and G-C-G-C sites in the rDNA coding regions and intervening sequences of Drosophila and the rDNA of other insects.
• Spacer sequences downstream of the 28S RNA coding region are part of the mouse rDNA transcription unit.
• Association of the RENT complex with nontranscribed and coding regions of rDNA and a regional requirement for the replication fork block protein Fob1 in rDNA silencing