A family of developmentally excised DNA elements in Tetrahymena is under selective pressure to maintain an open reading frame encoding an integrase-like protein. Nucleic Acids Res 2000 Nov 01;28(21):4105-12
Date
11/01/2000Pubmed ID
11058106Pubmed Central ID
PMC113129DOI
10.1093/nar/28.21.4105Scopus ID
2-s2.0-0034327418 (requires institutional sign-in at Scopus site) 16 CitationsAbstract
Tlr1 is a member of a family of approximately 20-30 DNA elements that undergo developmentally regulated excision during formation of the macronucleus in the ciliated protozoan TETRAHYMENA: Analysis of sequence internal to the right boundary of Tlr1 revealed the presence of a 2 kb open reading frame (ORF) encoding a deduced protein with similarity to retrotransposon integrases. The ORFs of five unique clones were sequenced. The ORFs have 98% sequence conservation and align without frameshifts, although one has an additional trinucleotide at codon 561. Nucleotide changes among the five clones are highly non-random with respect to the position in the codon and 93% of the nucleotide changes among the five clones encode identical or similar amino acids, suggesting that the ORF has evolved under selective pressure to preserve a functional protein. Nineteen T/C transitions in T/CAA and T/CAG codons suggest selection has occurred in the context of the TETRAHYMENA: genome, where TAA and TAG encode Gln. Similarities between the ORF and those encoding retrotransposon integrases suggest that the Tlr family of elements may encode a polynucleotide transferase. Possible roles for the protein in transposition of the elements within the micronuclear genome and/or their developmentally regulated excision from the macronucleus are discussed.
Author List
Gershan JA, Karrer KMMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAmino Acid Substitution
Animals
Blotting, Southern
Cloning, Molecular
Codon
Conserved Sequence
DNA, Protozoan
Gene Deletion
Gene Dosage
Gene Expression Regulation, Developmental
Genetic Code
Genome, Protozoan
Integrases
Micronucleus, Germline
Molecular Sequence Data
Multigene Family
Open Reading Frames
Recombination, Genetic
Restriction Mapping
Selection, Genetic
Sequence Alignment
Tetrahymena
Transposases
