A reverse transcriptase/maturase promotes splicing by binding at its own coding segment in a group II intron RNA.
Group II introns encode reverse transcriptases that promote RNA splicing (maturase activity) and then with the excised intron form a DNA endonuclease that mediates intron mobility by target DNA-primed reverse transcription (TPRT). Here, we show that the primary binding site for the maturase (LtrA) encoded by the Lactococcus lactis Ll.LtrB intron is within a region of intron domain IV that includes the start codon of the LtrA ORF. This binding is enhanced by other elements, particularly domain I and the EBS/IBS interactions, and helps position LtrA to initiate cDNA synthesis in the 3' exon as occurs during TPRT. Our results suggest how the maturase functions in RNA splicing and support the hypothesis that the reverse transcriptase coding region was derived from an independent genetic element that was inserted into a preexisting group II intron.
Wank
H
H
Department of Chemistry and Biochemistry, University of Texas at Austin 78712, USA.
SanFilippo
J
J
Singh
R N
RN
Matsuura
M
M
Lambowitz
A M
AM
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D018387:Codon, Initiator; D004251:DNA Transposable Elements; D004926:Escherichia coli; D005091:Exons; D007438:Introns; D007700:Kinetics; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D012326:RNA Splicing; D012194:RNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D018387:Codon, Initiator; D004251:DNA Transposable Elements; C099786:LtrB protein, Lactococcus lactis; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C066564:aI2 protein, S cerevisiae; C099785:LtrA protein, Lactococcus lactis; D012194:RNA-Directed DNA Polymerase