Nuclear group I introns in self-splicing and beyond

Abstract

Group I introns are a distinct class of RNA self-splicing introns with an ancient origin. All known group I introns present in eukaryote nuclei interrupt functional ribosomal RNA genes located in ribosomal DNA loci. The discovery of the Tetrahymena intron more than 30 years ago has been essential to our understanding of group I intron catalysis, higher-order RNA structure, and RNA folding, but other intron models have provided information about the biological role. Nuclear group I introns appear widespread among eukaryotic microorganisms, and the plasmodial slime molds (myxomycetes) contain an abundance of self-splicing introns. Here, we summarize the main conclusions from previous work on the Tetrahymena intron on RNA self-splicing catalysis as well as more recent work on myxomycete intron biology. Group I introns in myxomycetes that represent different evolutionary stages, biological roles, and functional settings are discussed.

Mitochondrial Group I Introns in Hexacorals Are Regulatory Genetic Elements

“…Similar obligatory group I introns have been noted in the chloroplast tRNA Leu gene of all green plants and in the nuclear LSU rRNA gene of all Physarales myxomycetes [50,51]. These obligatory mitochondrial, chloroplast, and nuclear introns are considered domesticated group I introns that may have gained new host-specific functions beyond self-splicing [21,25]. The mitochondrial ND5 mRNA stability has a key role in respiratory control in higher animals; it is tightly regulated and contains m 1 A base modification [52][53][54].…”

“…These introns sometimes even code for homing endonucleases, giving additional mobility to the ribozymes. The intron RNA processing reaction is catalyzed by the ribozyme, which folds into at least nine conserved paired segments (P1-P9), further organized into hallmark helical stacks named the catalytic domain, the substrate domain, and the scaffold domain ( Figure 1B) [23][24][25]. Group I intron sequences are removed from precursor transcripts in a guanosine-dependent two-step transesterification reaction, leading to exon ligation and intron excision [21].…”

Identification of Microalgae Producers of Commercially Important Compounds

“…In this sense and because the ribosomal DNA is inherited, introns from group I can be used as a phylogenetic marker [60]. By comparing the sequence of the 18S rDNA of the 33 selected microalgae for this work, it was possible to differentiate the species containing introns from those that did not (Figure 3.1).…”

Modulation of Gene Expression by Gene Architecture and Promoter Structure

“…Spliceosomal introns are the foremost discovered and well characterized introns, which are excised by spliceosome, a ribonucleoprotein complex [36,37]. Group I introns, widely present in mRNA, rRNA and tRNA of variety of organisms including algae, fungi, lower eukaryotes and few bacteria [38][39][40][41][42]. Similarly, group II introns are large autocatalytic ribozymes widely present in the mitochondria, chloroplast, plants, fungi, yeast and many bacteria, play major role in genome evolution [43][44][45][46].…”