New type of polyubiquitin-like genes with intein-like autoprocessing domains

Genome analysis of ciliates identified a new type of polyubiquitin-like genes. These contain tandem repeats of ubiquitin-like domains interspersed with autocatalytic intein-like domains. Inteins and related protein domains post-translationally process their own precursor proteins by protein-splicing, cleavage and ligation reactions. The structure of these polyubiquitin-like genes suggests their precursor products undergo maturation and conjugation in cis. This novel gene structure also illustrates the genetic modularity of ubiquitin-like and intein-like domains. Our suggested autoprocessing of ubiquitin-like polyproteins is a new potential general way for controlling protein functions.