A handful of intron-containing genes produces the lion's share of yeast mRNA

Abstract

Two studies have provided separate pieces of information that bear on the functional and evolutionary significance of introns in the budding yeast Saccharomyces cerevisiae (Holstege et al., 1998; Spingola et al., 1999). By the measure of the number of introns within its genes, budding yeast seems a disappointing eukaryote. Fewer than 250 of the more than 6,200 annotated genes are known to have introns, and fewer than 10 are known have more than one intron (Spingola et al., 1999). In contrast, metazoan genes are estimated to average nearly 10 introns, and the intronless gene is the exception rather than the rule. Although many essential yeast genes have introns, it would appear that introns are on the way out of the yeast genome, perhaps by a cDNA-directed homologous recombination mechanism proposed by Fink (1987).