title: Nanos1 functions as a translational repressor in the Xenopus germline.
abstract: Nanos family members have been shown to act as translational repressors in the Drosophila and Caenorhabditis elegans germline, but direct evidence is missing for a similar function in vertebrates. Using a tethered function assay, we show that Xenopus Nanos1 is a translational repressor and that association with the RNA is required for this repression. We identified a 14 amino acid region within the N-terminal domain of Nanos1 that is conserved in organisms as diverse as sponge and Human. The region is found in all vertebrates but notably lacking in Drosophila and C. elegans. Deletion and substitution analysis revealed that this conserved region was required for Nanos1 repressive activity. Consistent with this observation, deletion of this region was sufficient to prevent abnormal development that results from ectopic expression of Nanos1 in oocytes. Although Nanos1 can repress capped and polyadenylated RNAs, Nanos1 mediated repression did not require the targeted RNA to have a cap or to be polyadenylated. These results suggest that Nanos1 is capable of repressing translation by several different mechanisms. We found that Nanos1, like Drosophila Nanos, associates with cyclin B1 RNA in vivo indicating that some Nanos targets may be evolutionarily conserved. Nanos1 protein was detected and thus available to repress mRNAs while PGCs were in the endoderm, but was not observed in PGCs after this stage.
authors.affiliation: Department of Cell Biology and Anatomy, University of Miami School of Medicine, 1011 NW 15th St., Miami, FL 33136, USA.
authors.forename: Fangfang
authors.initials: F
authors.lastname: Lai
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhou
authors.forename: Xueting
authors.initials: X
authors.lastname: Luo
authors.forename: Josh
authors.initials: J
authors.lastname: Fox
authors.forename: Mary Lou
authors.initials: ML
authors.lastname: King
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002457:Cell Extracts; D017124:Conserved Sequence / Q000235:genetics; D056744:Cyclin B1 / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics*; D012313:RNA / Q000378:metabolism; D012315:RNA Caps / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D056744:Cyclin B1; D012315:RNA Caps; D012097:Repressor Proteins; D029867:Xenopus Proteins; C558784:nanos1 protein, Xenopus; D012313:RNA