The nuclear-encoded inteins of fungi.

An intein is a protein sequence embedded within a precursor protein that is excised during protein maturation. Inteins were first found encoded in the VMA gene of Saccharomyces cerevisiae. Subsequently, they have been found in diverse organisms (eukaryotes, archaea, eubacteria and viruses). The VMA intein has been found in various saccharomycete yeasts but not in other fungi. Different inteins have now been found widely in the fungi (ascomycetes, basidiomycetes, zygomycetes and chytrids) and in diverse proteins. A protein distantly related to inteins, but closely related to metazoan hedgehog proteins, has been described from Glomeromycota. Many of the newly described inteins contain homing endonucleases and some of these are apparently active. The enlarged fungal intein data set permits insight into the evolution of inteins, including the role of horizontal transfer in their persistence. The diverse fungal inteins provide a resource for biotechnology using their protein splicing or homing endonuclease capabilities.