We have characterized the splicing products formed in vitro from RNA derived from the mobile group I intron in the nuclear rDNA of Physarum polycephalum, Pp LSU 3. This intron is a close relative of the well known Tetrahymena intron Tt LSU 1, being inserted at exactly the same position in the rDNA and sharing about 90% sequence identity with Tt LSU 1 in the conserved elements characteristic of ...

Circularly permuted group I intron precursor RNAs, containing end-to-end fused exons which interrupt half-intron sequences, were generated and tested for self-splicing activity. An autocatalytic RNA can form when the primary order of essential intron sequence elements, splice sites, and exons are permuted in this manner. Covalent attachment of guanosine to the 5' half-intron product, and accura...

The yeast mitochondrial DNA group II introns aI1 and aI2 are retroelements that insert site specifically into intronless alleles by a process called homing. Here, we used patterns of flanking marker coconversion in crosses with wild-type and mutant aI2 introns to distinguish three coexisting homing pathways: two that were reverse transcriptase (RT) dependent (retrohoming) and one that was RT in...

Homing endonuclease genes are mobile elements that promote their duplication into cognate sites that lack the endonuclease gene [1, 2]. The homing endonuclease initiates this event through site-specific DNA cleavage. Copying of the endonuclease gene follows as a consequence of DNA repair. A genome containing a homing endonuclease gene is subject to self-cleavage. Protection is accomplished thro...

Group I introns were discovered inserted at the same position in the nuclear small-subunit ribosomal DNA (nuc-ssu-rDNA) in several species of homobasidiomycetes (mushroom-forming fungi). Based on conserved intron sequences, a pair of intron-specific primers was designed for PCR amplification and sequencing of intron-containing rDNA repeats. Using the intron-specific primers together with flanki...

The CRM domain is a recently recognized RNA binding domain found in three group II intron splicing factors in chloroplasts, in a bacterial protein that associates with ribosome precursors, and in a family of uncharacterized proteins in plants. To elucidate the functional repertoire of proteins with CRM domains, we studied CFM2 (for CRM Family Member 2), which harbors four CRM domains. RNA coimm...

Excision of the bacterial group II intron RmInt1 has been demonstrated in vivo, resulting in the formation of both intron lariat and putative intron RNA circles. We show here that the bulged adenosine in domain VI of RmInt1 is required for splicing via the branching pathway, but branch site mutants produce small numbers of RNA molecules in which the first G residue of the intron is linked to th...