title: A homologue of CROC-1 in a ciliated protist (Sterkiella histriomuscorum) testifies to the ancient origin of the ubiquitin-conjugating enzyme variant family.
abstract: Resting cysts of Sterkiella histriomuscorum (Ciliophora, Oxytrichidae) have been shown to contain messenger RNA, one of which codes for a protein significantly similar to CROC-1. CROC-1 is a human regulatory protein capable of transactivating the promoter of c-fos and belongs to a newly characterized family of ubiquitin-conjugating enzyme (E2) variants (UEV). We have determined the corresponding macronuclear gene sequence, which is the first protistan UEV sequence available. The phylogenetic analysis indicates the deep separation and solid clustering of all the UEV sequences within the E2 tree showing the ancient origin of these regulatory genes and their high structural conservation during evolution. Furthermore, overexpression of the ciliate UEV is able to rescue the Saccharomyces cerevisiae mms2 null mutant from killing by DNA damaging agents, implying that the UEV family proteins are functionally conserved. In S. histriomuscorum, expression of UEV is correlated with the growth of the cells as transcripts are present in excysting and vegetative cells but are rapidly down-regulated during starvation. These data support the high conservation of the UEV family in eukaryotes, and a regulatory role of the gene is discussed in relation to known functions of UEVs. This analysis may promote the search for homologues of other regulatory genes (metazoan regulators of differentiation) in ciliates.
authors.affiliation: Laboratoire de Biologie Cellulaire 4, (UPRES-A 8080), Bâtiment 444, Université Paris-Sud, 91405 Orsay Cedex, France.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Villalobo
authors.forename: Loïc
authors.initials: L
authors.lastname: Morin
authors.forename: Clara
authors.initials: C
authors.lastname: Moch
authors.forename: Rachel
authors.initials: R
authors.lastname: Lescasse
authors.forename: Michelle
authors.initials: M
authors.lastname: Hanna
authors.forename: Wei
authors.initials: W
authors.lastname: Xiao
authors.forename: Anne
authors.initials: A
authors.lastname: Baroin-Tourancheau
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016798:Ciliophora / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D003001:Cloning, Molecular; D016000:Cluster Analysis; D017124:Conserved Sequence; D019143:Evolution, Molecular; D006801:Humans; D007438:Introns / Q000235:genetics; D008025:Ligases / Q000737:chemistry / Q000235:genetics; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors; D024363:Transcription Initiation Site; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes
chemical_list: D009687:Nuclear Proteins; D015800:Protozoan Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D014157:Transcription Factors; D025801:Ubiquitin; C471624:UBE2V1 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D008025:Ligases