Beyond homing: competition between intron endonucleases confers a selective advantage on flanking genetic markers

Article Abstract:

Two Bacillus subtilis bacteriophages, SPO1 and SP82, have been analyzed for the activities of their introns that encode endonucleases. The bacteriophages' group I intron present in DNA polymerase genes, which encode the endonucleases (I-HmuI for SPO1 and I-HmuII for SP82), share similar structures such as a common set of base-paired structural elements, P1-P9, that forms the active ribozyme, and an open reading frame inserted at the loop of structural element P8. The SP82's intron-encoded endonuclease has shown the ability to propagate itself by flanking markers into the genome of a closely related phage.

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A tyrosyl-tRNA synthetase recognizes a conserved tRNA-like structural motif in the group I intron catalytic core

Article Abstract:

Three-dimensional models based on chemical footprinting and ribonucleic acid (RNA)-footprinting data were constructed to determine the role of mitochondrial tyrosyl transfer RNA synthetase (CYT-18) in intron splicing. Analysis of Neurospora crassa CYT-18 binding sites in three-dimensional models indicated the presence of an extended overlap between the transfer RNA and the catalytic core of the group I intron. Furthermore, the similarity of the group I introns and the tRNAs exhibited the evolutionary relationship between RNA-splicing factors and cellular RNA-binding proteins.

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A group II intron RNA is a catalytic component of a DNA endonuclease involved in intron mobility

Article Abstract:

The mobility of the mitochondrial DNA group II intron al2 in yeast occurs via a DNA endonuclease containing al2RNA and the al2 proteins. The al2 protein cleaves the antisense strand while the al2RNA catalyzes the cleavage of the sense strand of the recipient DNA. The sense strand cleavage occurs by reverse splicing and stabilization of the active intron. The reverse splicing is fully suppressed by a mutation in the maturase domain and by the removal of Zn domain through truncation. The impact of removing the C-terminal region of the Zn domain is discussed.

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