Introns of Entamoeba histolytica and Entamoeba dispar

The genome of Entamoeba histolytica is considered to possess very few inter vening sequences (introns), as only 5 intron-containing genes from this pro tozoan parasite have been reported so far. However, while sequencing a numb er of genomic contigs as well as three independent genes coding for ribosom al protein L27a, we have identified 9 additional intron-containing genes of E. histolytica and the closely related species Entamoeba dispar, indicatin g that introns are more common in these organisms than previously suggested . The various amoeba introns are relatively short comprising between 46 and 115 nucleotides only and have a higher AT-content compared to the correspo nding exon sequences. In contrast to higher eukaryotes, amoeba introns do n ot contain a well-conserved branch point consensus, and have extended donor and acceptor splice sites of the sequences GTTTGTT and TAG, respectively. Consistent with the close phylogenetic relationship of E. histolytica and E . dispar, the position and length of introns is; conserved between the two species but the degree of sequence identity is reduced compared to ortholog ous coding regions.