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Gene Review

AI2  -  intron-encoded reverse transcriptase aI2

Saccharomyces cerevisiae S288c

Synonyms: Q0055, aI2
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High impact information on AI2

  • 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].
  • Reverse transcription of aI2-containing pre-mRNA is primed by the antisense strand cleaved in exon 3 and results in cotransfer of the intron and flanking exon sequences [2].
  • RNA isolated from yeast mitochondria also contains circles, indicating that at least one group II intron (aI2) forms circles in vivo [3].
  • 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 independent [4].
  • Efficient mobility is dependent on both the RT activity of the aI2-encoded protein and a separate function, a putative DNA endonuclease, that is associated with the Zn2+ finger-like region of the intron reading frame [5].

Biological context of AI2

  • Northern blot analyses of mitochondrial transcripts indicate cox24 null mutants to be blocked in processing of introns aI2 and aI3 [6].
  • 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 [7].
  • 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 [7].
  • (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 [8].
  • Non-denaturing gel electrophoresis and activity assays show that the aI2 reverse transcriptase is associated predominantly with the excised intron RNA, while a smaller amount is associated with unspliced precursor RNA, as expected from the role of the protein in RNA splicing [9].

Other interactions of AI2


  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. Group II intron mobility occurs by target DNA-primed reverse transcription. Zimmerly, S., Guo, H., Perlman, P.S., Lambowitz, A.M. Cell (1995) [Pubmed]
  3. Excision of group II introns as circles. Murray, H.L., Mikheeva, S., Coljee, V.W., Turczyk, B.M., Donahue, W.F., Bar-Shalom, A., Jarrell, K.A. Mol. Cell (2001) [Pubmed]
  4. Multiple homing pathways used by yeast mitochondrial group II introns. Eskes, R., Liu, L., Ma, H., Chao, M.Y., Dickson, L., Lambowitz, A.M., Perlman, P.S. Mol. Cell. Biol. (2000) [Pubmed]
  5. Mobile group II introns of yeast mitochondrial DNA are novel site-specific retroelements. Moran, J.V., Zimmerly, S., Eskes, R., Kennell, J.C., Lambowitz, A.M., Butow, R.A., Perlman, P.S. Mol. Cell. Biol. (1995) [Pubmed]
  6. COX24 codes for a mitochondrial protein required for processing of the COX1 transcript. Barros, M.H., Myers, A.M., Van Driesche, S., Tzagoloff, A. J. Biol. Chem. (2006) [Pubmed]
  7. 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]
  8. 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]
  9. Group II intron reverse transcriptase in yeast mitochondria. Stabilization and regulation of reverse transcriptase activity by the intron RNA. Zimmerly, S., Moran, J.V., Perlman, P.S., Lambowitz, A.M. J. Mol. Biol. (1999) [Pubmed]
  10. 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]
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