Fig. 11

Evolutionary switch from DCD to eTudor domains. Cleavage and polyadenylation specificity factor 30 (CPSF30) orthologs contain YTH and DCD domains in many heterokont species, and a CAPAM-like putative mRNA methyltransferase containing a DCD domain was detected in a haptophyte species. Multi-eTudor domain proteins evolved from Tudor-SN to produce the family of essential piRNA pathway factors in metazoans, but their ancestry is poorly understood. The eTudor-DCD proteins in choanoflagellates and eTudor-YTH proteins in corals clarify the evolutionary history of the eTudor family. a Domain organization of representative orthologs of CPSF30 from budding yeast, human, Arabidopsis, and the pathogenic oomycete S. diclina, as well as a CAPAM-like putative mRNA methyltransferase from C. tobinii which contains a DCD domain and was the only example detected. The RefSeq protein accession numbers are indicated. Zinc finger (Znf) domains are labeled with their type. b The core Tudor domain inherited from prokaryotes and present in histone-binding proteins is shown in blue. An N-terminal α-helix conserved in SMN-like proteins and incorporated into the eTudor domain is shown in green. The SNase domain that the SMN-like Tudor domain inserted into is shown in orange, with sections at both termini of the resulting eTudor domain that fold around the inserted Tudor domain to retain the original SNase structure [59]. A multi-eTudor protein is shown interacting with dimethylarginine residues in RGRGRG motifs at the N-termini of two Piwi-related Argonautes. Such motifs are conserved sites of arginine methylation in the Argonautes, as well as Sm proteins bound by the Tudor domains in SMN and Tudor-SN. c Domain organization of two choanoflagellate eTudor-DCD proteins and a representative coral eTudor-YTH protein. The species and GenBank or RefSeq protein accession numbers, or identifiers from the predicted protein dataset published by Richter et al. are indicated (Additional file 3: Dataset 2). 5′ partial proteins predicted from transcriptome sequencing are marked at the incomplete terminus. Zinc finger (Znf) domains are labeled with their type