The function of introns

Abstract

The intron-exon architecture of many eukaryotic genes raises the intriguing question of whether this unique organization serves any function, or is it simply a result of the spread of functionless introns in eukaryotic genomes. In this review, we show that introns in contemporary species fulfill a broad spectrum of functions, and are involved in virtually every step of mRNA processing. We propose that this great diversity of intronic functions supports the notion that introns were indeed selfish elements in early eukaryotes, but then independently gained numerous functions in different eukaryotic lineages. We suggest a novel criterion of evolutionary conservation, dubbed intron positional conservation, which can identify functional introns.

Keywords: exon-junction complex; expression regulation; gene architecture; intron function; intron positional conservation; intron–exon structure; non-coding RNAs; splicing.

Figure 1

Schematic description of the five phases of an intron life span.

Figure 2

Schematic description of the different roles played by the exon-junction complex (EJC).

Figure 3

(A) Intron position is defined as the point of intron insertion along the mRNA. (B) Comparison of intron positions between orthologous genes.