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AI1  -  intron-encoded reverse transcriptase aI1

Saccharomyces cerevisiae S288c

Synonyms: Q0050, aI1
 
 
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High impact information on AI1

  • For aI2, sense-strand cleavage occurs mainly by a partial reverse splicing reaction, whereas for aI1, complete reverse splicing occurs, leading to insertion of the linear intron RNA into double-stranded DNA [1].
  • Here, we show that aI1 homing and reverse splicing depend on the EBS1 (RNA)/IBS1(DNA) pairing and that target specificity can be changed by compensatory changes in the target site and the donor intron [1].
  • Introns aI1 and aI2 found in the gene COX1 in yeast mitochondria encode reverse transcriptases which promote site-specific insertion of the intron into intronless alleles ('homing') [2].
  • Transposition of group II intron aI1 in yeast and invasion of mitochondrial genes at new locations [3].
  • AI1 RNA is most reactive at 37-42 degrees C, as compared with 45 degrees C for the group IIB introns; and it lacks the KCl- or NH4Cl-dependent spliced-exon reopening reaction that is evident for the self-splicing group IIB introns of yeast mitochondria [4].
 

Biological context of AI1

  • RNA splicing in yeast mitochondria: DNA sequence analysis of mit- mutants deficient in the excision of introns aI1 and aI2 of the gene for subunit I of cytochrome c oxidase [5].
  • (1982), is controlled by the activity of the maturases encoded by their respective ORFs and that the translation of the aI2 maturase depends on the previous excision of aI1 IVS [6].
  • RNA blot analysis shows that in addition to a reduced (mutant M15-190) or blocked (mutant M12-193) excision of the mutated intron aI1, the mutants are unable to excise the adjacent aI2 intron, the reading frame of which displays an amino acid sequence similarity to aI1 [5].
  • The mobile group II introns aI1 and aI2 of yeast mtDNA encode endonuclease activities that cleave intronless DNA target sites to initiate mobility by target DNA-primed reverse transcription [1].
  • Like the group IIB intron aI5 gamma, the domain 4 of aI1 can be largely deleted in cis, without blocking splicing; also, trans-splicing of half molecules interrupted in domain 4 occurs [4].
 

Associations of AI1 with chemical compounds

  • Unlike the group IIB introns, aI1 is inactive in 10 mM Mg2+ (including spermidine) and requires much higher levels of Mg2+ and added salts (1M NH4Cl or KCl or 2M (NH4)2SO4) for ready detection of splicing activity [4].
 

Other interactions of AI1

  • Mitochondrial introns aI1 and/or aI2 are needed for the in vivo deletion of intervening sequences [7].
  • The aI1 endonuclease activity, which catalyzes the DNA cleavage and reverse splicing reactions, is associated with ribonucleoprotein particles containing the intron-encoded protein and the excised intron RNA [8].
 

Analytical, diagnostic and therapeutic context of AI1

  • We used polymerase chain reaction (PCR) techniques to detect infrequent rearrangements in mtDNA and report here on duplicative IVS transposition, twintron formation (e.g. bI1 insertion into another bI1 intron), and IVS insertions at canonical 5' exon-intron borders in S. pombe (cob1-bI1) and in S. cerevisiae (cox1-aI1) [9].

References

  1. Mobility of yeast mitochondrial group II introns: engineering a new site specificity and retrohoming via full reverse splicing. Eskes, R., Yang, J., Lambowitz, A.M., Perlman, P.S. Cell (1997) [Pubmed]
  2. Efficient integration of an intron RNA into double-stranded DNA by reverse splicing. Yang, J., Zimmerly, S., Perlman, P.S., Lambowitz, A.M. Nature (1996) [Pubmed]
  3. Transposition of group II intron aI1 in yeast and invasion of mitochondrial genes at new locations. Mueller, M.W., Allmaier, M., Eskes, R., Schweyen, R.J. Nature (1993) [Pubmed]
  4. A maturase-encoding group IIA intron of yeast mitochondria self-splices in vitro. Hebbar, S.K., Belcher, S.M., Perlman, P.S. Nucleic Acids Res. (1992) [Pubmed]
  5. RNA splicing in yeast mitochondria: DNA sequence analysis of mit- mutants deficient in the excision of introns aI1 and aI2 of the gene for subunit I of cytochrome c oxidase. van der Veen, R., de Haan, M., Grivell, L.A. Curr. Genet. (1988) [Pubmed]
  6. Expression of the mitochondrial split gene coding for cytochrome oxidase subunit I in S. cerevisiae: RNA splicing pathway. Carignani, G., Netter, P., Bergantino, E., Robineau, S. Curr. Genet. (1986) [Pubmed]
  7. Mitochondrial introns aI1 and/or aI2 are needed for the in vivo deletion of intervening sequences. Levra-Juillet, E., Boulet, A., Séraphin, B., Simon, M., Faye, G. Mol. Gen. Genet. (1989) [Pubmed]
  8. Group II intron mobility in yeast mitochondria: target DNA-primed reverse transcription activity of aI1 and reverse splicing into DNA transposition sites in vitro. Yang, J., Mohr, G., Perlman, P.S., Lambowitz, A.M. J. Mol. Biol. (1998) [Pubmed]
  9. Transposable group II introns in fission and budding yeast. Site-specific genomic instabilities and formation of group II IVS plDNAs. Schmidt, W.M., Schweyen, R.J., Wolf, K., Mueller, M.W. J. Mol. Biol. (1994) [Pubmed]
 
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