 Another twintron complex was detected at position mS1247 of the "Chaetomium thermophilumhere" mt-rns gene, a group IIA1 intron invaded the open reading frame embedded within a group IC2 intron.The mS1247 twintron represents the first recorded fungal mitochondrial mixed twintron consisting of group II intron as an internal intron and a group I intron as an external intron.In mS1247 twintron, splicing of the internal group IIA1 intron reconstitutes the open reading frame encoded within the group IC2 intron and thus facilitates the expression of the encoded homing endonuclease.