title: Myb genes in ciliates: a common origin with the myb protooncogene?
abstract: In animals, the protooncogene myb family is characterized by a DNA-binding domain (so-called MYB domain), which consists of 3 imperfect tandem repeats of a helix-turn-helix motif. Homologous genes have been characterized in plants and also in Dictyostelium discoideum. However, in plants, the myb family is more diverse and displays 2 types of MYB domains: the animal-like 3 repeats (MYB-3R) and the 2 repeats (MYB-2R) domains. The question is therefore raised as to the putative existence of genes with MYB-3R and/or MYB-2R domains in their last common unicellular ancestor. Here, we present evidence that in ciliates like in plants, both types of domain exist. A gene having a MYB-3R domain has been identified in the oxytrichid Sterkiella histriomuscorum and a gene having a MYB-2R domain has been identified in the euplotid Euplotes aediculatus. Both genes are expressed during the vegetative growth of the cells. A conserved intron exists in the gene of Sterkiella and phylogenetical analyses show that the 2 ciliate genes belong to the myb protooncogene family as deeply split lineages. This is the first report of a myb homolog in a ciliated protist, thus, confirming its origin in strict unicellular eukaryotes.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016798:Ciliophora / Q000235:genetics* / Q000254:growth & development; D019143:Evolution, Molecular; D020570:Genes, myb; D008969:Molecular Sequence Data; D010802:Phylogeny; D020598:Proto-Oncogene Proteins c-myb / Q000737:chemistry / Q000235:genetics*; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D020080:Tandem Repeat Sequences
chemical_list: D020598:Proto-Oncogene Proteins c-myb; D015800:Protozoan Proteins