Myb Genes in Ciliates: A Common Origin with the myb Protooncogene?

• Published in: Protist Vol. 154; no. 2; pp. 229 - 238
• Main Authors: Yang, T.i.e., Perasso, Roland, Baroin-Tourancheau, Anne
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.07.2003; Elsevier Science Ltd
• Subjects: Amino Acid Sequence; Animals; ciliates; Ciliophora - genetics; Ciliophora - growth & development; DNA-binding domain; Evolution, Molecular; Genes, myb; Molecular Sequence Data; myb; Phylogeny; Proto-Oncogene Proteins c-myb - chemistry; Proto-Oncogene Proteins c-myb - genetics; Protozoan Proteins - chemistry; Protozoan Proteins - genetics; Reverse Transcriptase Polymerase Chain Reaction; Sequence Alignment; Tandem Repeat Sequences; phylogeny; DNA-binding domain; ciliates; myb
• ISSN: 1434-4610; 1618-0941
• DOI: 10.1078/143446103322166527

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.