An intron in the thymidylate synthase gene of Bacillus bacteriophage beta 22: evidence for independent evolution of a gene, its group I intron, and the intron open reading frame.

AUTOR(ES)

Bechhofer, D H

RESUMO

The thymidylate synthase gene (thy) (EC 2.1.1.45) of Bacillus subtilis bacteriophage beta 22 has a self-splicing, group I intron inserted into a highly conserved region of the coding sequence. The intron is very similar to one that is inserted 21 bp further downstream in the homologous thymidylate synthase gene (td) of Escherichia coli bacteriophage T4. In contrast, the amino acid sequences of the bacteriophage thymidylate synthases are highly divergent. The beta 22 intron has a fragmentary open reading frame (ORF) that encodes a putative helix-turn-helix DNA-binding motif, similar to one at the carboxyl terminus of the homing endonuclease (I-TevI) encoded by the T4 td intron. The td ORF and the thy ORF fragments are inserted into different regions of their respective intron structures. These results suggest that the thymidylate synthase genes, their introns, and their respective intron-ORFs all have separate evolutionary histories and that the acquisition of the intron could not have occurred by a simple homing event.

Documentos Relacionados

• Polyadenylylation signal of the mouse thymidylate synthase gene was created by insertion of an L1 repetitive element downstream of the open reading frame.
• Bacterial Thymidylate Synthase with Intein, Group II Intron, and Distinctive ThyX Motifs
• Light modulation of ferredoxin mRNA abundance requires an open reading frame.
• Mutational analysis of the human immunodeficiency virus vpr open reading frame.
• Nucleotide sequence of the HPV16 L1 open reading frame.