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EMBO J. Feb 1991; 10(2): 433–442.
PMCID: PMC452664

Group II twintron: an intron within an intron in a chloroplast cytochrome b-559 gene.


The psbF gene of chloroplast DNAs encodes the beta-subunit of cytochrome b-559 of the photosystem II reaction center. The psbF locus of Euglena gracilis chloroplast DNA has an unusual 1042 nt group II intron that appears to be formed from the insertion of one group II intron into structural domain V of a second group II intron. Using both direct primer extension cDNA sequencing and cDNA cloning and sequencing, we have determined that a 618 nt internal intron is first excised from the 1042 nt intron of psbF pre-mRNA, resulting in a partially spliced pre-mRNA containing a 424 nt group II intron with a spliced domain V. The 424 nt intron is then removed to yield the mature psbF mRNA. Therefore, the 1042 nt intron of psbF is a group II intron within another group II intron. We use the term 'twintron' to define this new type of genetic element. Intermediates in the splicing pathway were detected by northern hybridization. Splicing of both the internal and external introns occurs via lariat intermediates. Twintron splicing was found to proceed by a sequential pathway, the internal intron being removed prior to the excision of the external intron. A possible mechanism for twintron formation by intron transposition is discussed.

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  • Augustin S, Müller MW, Schweyen RJ. Reverse self-splicing of group II intron RNAs in vitro. Nature. 1990 Jan 25;343(6256):383–386. [PubMed]
  • Bass BL, Cech TR. Ribozyme inhibitors: deoxyguanosine and dideoxyguanosine are competitive inhibitors of self-splicing of the Tetrahymena ribosomal ribonucleic acid precursor. Biochemistry. 1986 Aug 12;25(16):4473–4477. [PubMed]
  • Boynton JE, Gillham NW, Harris EH, Hosler JP, Johnson AM, Jones AR, Randolph-Anderson BL, Robertson D, Klein TM, Shark KB, et al. Chloroplast transformation in Chlamydomonas with high velocity microprojectiles. Science. 1988 Jun 10;240(4858):1534–1538. [PubMed]
  • Carrillo N, Seyer P, Tyagi A, Herrmann RG. Cytochrome b-559 genes from Oenothera hookeri and Nicotiana tabacum show a remarkably high degree of conservation as compared to spinach. The enigma of cytochrome b-559: highly conserved genes and proteins but no known function. Curr Genet. 1986;10(8):619–624. [PubMed]
  • Cech TR. The generality of self-splicing RNA: relationship to nuclear mRNA splicing. Cell. 1986 Jan 31;44(2):207–210. [PubMed]
  • Cech TR. Conserved sequences and structures of group I introns: building an active site for RNA catalysis--a review. Gene. 1988 Dec 20;73(2):259–271. [PubMed]
  • Chakhmakhcheva OG, Andreeva AV, Buryakova AA, Reverdatto SV, Efimov VA. Nucleotide sequence of the barley chloroplast psbE, psbF genes and flanking regions. Nucleic Acids Res. 1989 Apr 11;17(7):2858–2858. [PMC free article] [PubMed]
  • Christopher DA, Hallick RB. Euglena gracilis chloroplast ribosomal protein operon: a new chloroplast gene for ribosomal protein L5 and description of a novel organelle intron category designated group III. Nucleic Acids Res. 1989 Oct 11;17(19):7591–7608. [PMC free article] [PubMed]
  • Christopher DA, Hallick RB. Complex RNA maturation pathway for a chloroplast ribosomal protein operon with an internal tRNA cistron. Plant Cell. 1990 Jul;2(7):659–671. [PMC free article] [PubMed]
  • Cushman JC, Christopher DA, Little MC, Hallick RB, Price CA. Organization of the psbE, psbF, orf38, and orf42 gene loci on the Euglena gracilis chloroplast genome. Curr Genet. 1988 Feb;13(2):173–180. [PubMed]
  • Cushman JC, Hallick RB, Price CA. The two genes for the P700 chlorophyll a apoproteins on the Euglena gracilis chloroplast genome contain multiple introns. Curr Genet. 1988 Feb;13(2):159–171. [PubMed]
  • Gingrich JC, Hallick RB. The Euglena gracilis chloroplast ribulose-1,5-bisphosphate carboxylase gene. I. Complete DNA sequence and analysis of the nine intervening sequences. J Biol Chem. 1985 Dec 25;260(30):16156–16161. [PubMed]
  • Grabowski PJ, Padgett RA, Sharp PA. Messenger RNA splicing in vitro: an excised intervening sequence and a potential intermediate. Cell. 1984 Jun;37(2):415–427. [PubMed]
  • Haley J, Bogorad L. Alternative promoters are used for genes within maize chloroplast polycistronic transcription units. Plant Cell. 1990 Apr;2(4):323–333. [PMC free article] [PubMed]
  • Ikeuchi M, Koike H, Inoue Y. N-terminal sequencing of low-molecular-mass components in cyanobacterial photosystem II core complex. Two components correspond to unidentified open reading frames of plant chloroplast DNA. FEBS Lett. 1989 Aug 14;253(1-2):178–182. [PubMed]
  • Jacquier A, Michel F. Multiple exon-binding sites in class II self-splicing introns. Cell. 1987 Jul 3;50(1):17–29. [PubMed]
  • Jarrell KA, Dietrich RC, Perlman PS. Group II intron domain 5 facilitates a trans-splicing reaction. Mol Cell Biol. 1988 Jun;8(6):2361–2366. [PMC free article] [PubMed]
  • Johnston SA, Anziano PQ, Shark K, Sanford JC, Butow RA. Mitochondrial transformation in yeast by bombardment with microprojectiles. Science. 1988 Jun 10;240(4858):1538–1541. [PubMed]
  • Koller B, Clarke J, Delius H. The structure of precursor mRNAs and of excised intron RNAs in chloroplasts of Euglena gracilis. EMBO J. 1985 Oct;4(10):2445–2450. [PMC free article] [PubMed]
  • Kolosov VL, Klezovich ON, Abdulaev NG, Zolosharev AS. Fotosistema II rzhi. Nukleotidnaia posledovatelnost' genov psbE, psbF, psbL i OPC40 khloroplastnoi DNK. Bioorg Khim. 1989 Sep;15(9):1284–1286. [PubMed]
  • Margolis J, Kenrick KG. Polyacrylamide gel electrophoresis in a continuous molecular sieve gradient. Anal Biochem. 1968 Oct 24;25(1):347–362. [PubMed]
  • Michel F, Jacquier A, Dujon B. Comparison of fungal mitochondrial introns reveals extensive homologies in RNA secondary structure. Biochimie. 1982 Oct;64(10):867–881. [PubMed]
  • Michel F, Dujon B. Conservation of RNA secondary structures in two intron families including mitochondrial-, chloroplast- and nuclear-encoded members. EMBO J. 1983;2(1):33–38. [PMC free article] [PubMed]
  • Michel F, Umesono K, Ozeki H. Comparative and functional anatomy of group II catalytic introns--a review. Gene. 1989 Oct 15;82(1):5–30. [PubMed]
  • Nanba O, Satoh K. Isolation of a photosystem II reaction center consisting of D-1 and D-2 polypeptides and cytochrome b-559. Proc Natl Acad Sci U S A. 1987 Jan;84(1):109–112. [PMC free article] [PubMed]
  • Pakrasi HB, Williams JG, Arntzen CJ. Targeted mutagenesis of the psbE and psbF genes blocks photosynthetic electron transport: evidence for a functional role of cytochrome b559 in photosystem II. EMBO J. 1988 Feb;7(2):325–332. [PMC free article] [PubMed]
  • Peebles CL, Perlman PS, Mecklenburg KL, Petrillo ML, Tabor JH, Jarrell KA, Cheng HL. A self-splicing RNA excises an intron lariat. Cell. 1986 Jan 31;44(2):213–223. [PubMed]
  • Schnare MN, Gray MW. Sixteen discrete RNA components in the cytoplasmic ribosome of Euglena gracilis. J Mol Biol. 1990 Sep 5;215(1):73–83. [PubMed]
  • Shinozaki K, Ohme M, Tanaka M, Wakasugi T, Hayashida N, Matsubayashi T, Zaita N, Chunwongse J, Obokata J, Yamaguchi-Shinozaki K, et al. The complete nucleotide sequence of the tobacco chloroplast genome: its gene organization and expression. EMBO J. 1986 Sep;5(9):2043–2049. [PMC free article] [PubMed]
  • Smith CW, Patton JG, Nadal-Ginard B. Alternative splicing in the control of gene expression. Annu Rev Genet. 1989;23:527–577. [PubMed]
  • Tae GS, Black MT, Cramer WA, Vallon O, Bogorad L. Thylakoid membrane protein topography: transmembrane orientation of the chloroplast cytochrome b-559 psbE gene product. Biochemistry. 1988 Dec 27;27(26):9075–9080. [PubMed]
  • Tae GS, Cramer WA. Lumen-side topography of the alpha-subunit of the chloroplast cytochrome b-559. FEBS Lett. 1989 Dec 18;259(1):161–164. [PubMed]
  • van der Veen R, Arnberg AC, van der Horst G, Bonen L, Tabak HF, Grivell LA. Excised group II introns in yeast mitochondria are lariats and can be formed by self-splicing in vitro. Cell. 1986 Jan 31;44(2):225–234. [PubMed]

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