Inteins and introns within the prp8 -gene of four Eupenicillium species.

Inteins are protein-intervening sequences that are translated with the host protein and can self-excise themselves post-translationally in an autocatalytic process. The flanking regions--called exteins--are then re-ligated with a new peptide bond, resulting in a mature host protein. Previously, we have identified inteins in the highly conserved 3.2 region of the PRP8 protein from species of the genus Penicillium. These inteins are integrated at the same position as that which has recently been described in PRP8 proteins from different strains of Cryptococcus neoformans and several ascomycetes. In this study, we investigated the presence of PRP8 inteins in four members of the genus Eupenicillium. Two species of this genus, Eupenicillium crustaceum and Eupenicillium baarnense, contain an intein at the same insertion site. Both inteins are mini-inteins and undergo self-splicing when heterologously expressed with a model host protein in Escherichia coli. Interestingly, we identified introns in the prp8-sequence encoding the 3.2 regions of the PRP8 protein in Eupenicillium meridianum and Eupenicillium terrenum. The introns are located 13 bps and 15 bps downstream of the putative intein insertion site. Here, we consider that the lack of inteins in these two species might be due to the prevention of endonuclease-mediated intein propagation in the intron-containing prp8-sequences.