Alternative splicing of a group II intron in a surface layer protein gene in Clostridium tetani

Date
2013-10
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford Journals
Abstract
Group II introns are ribozymes and retroelements found in bacteria, and are thought to have been the ancestors of nuclear pre-mRNA introns. Whereas nuclear introns undergo prolific alternative splicing in some species, group II introns are not known to carry out equivalent reactions. Here we report a group II intron in the human pathogen Clostridium tetani, which undergoes four alternative splicing reactions in vivo. Together with unspliced transcript, five mRNAs are produced, each encoding a distinct surface layer protein isoform. Correct fusion of exon reading frames requires a shifted 5' splice site located 8 nt upstream of the canonical boundary motif. The shifted junction is accomplished by an altered IBS1-EBS1 pairing between the intron and 5' exon. Growth of C. tetani under a variety of conditions did not result in large changes in alternative splicing levels, raising the possibility that alternative splicing is constitutive. This work demonstrates a novel type of gene organization and regulation in bacteria, and provides an additional parallel between group II and nuclear pre-mRNA introns.
Description
Keywords
Citation
McNeil, B.A., Simon, D.M., Zimmerly, S. (2014) Alternative splicing of a group II intron in a surface layer protein gene in Clostridium tetani. Nucleic Acids Research 42:1959-1969. doi: 10.1093/nar/gkt1053