NANOS-3 and FBF proteins physically interact to control the sperm-oocyte switch in Caenorhabditis elegans.
BACKGROUND
The Caenorhabditis elegans FBF protein and its Drosophila relative, Pumilio, define a large family of eukaryotic RNA-binding proteins. By binding regulatory elements in the 3' untranslated regions (UTRs) of their cognate RNAs, FBF and Pumilio have key post-transcriptional roles in early developmental decisions. In C. elegans, FBF is required for repression of fem-3 mRNA to achieve the hermaphrodite switch from spermatogenesis to oogenesis.


RESULTS
We report here that FBF and NANOS-3 (NOS-3), one of three C. elegans Nanos homologs, interact with each other in both yeast two-hybrid and in vitro assays. We have delineated the portions of each protein required for this interaction. Worms lacking nanos function were derived either by RNA-mediated interference (nos-1 and nos-2) or by use of a deletion mutant (nos-3). The roles of the three nos genes overlap during germ-line development. In certain nos-deficient animals, the hermaphrodite sperm-oocyte switch was defective, leading to the production of excess sperm and no oocytes. In other nos-deficient animals, the entire germ line died during larval development. This germ-line death did not require CED-3, a protease required for apoptosis.


CONCLUSIONS
The data suggest that NOS-3 participates in the sperm-oocyte switch through its physical interaction with FBF, forming a regulatory complex that controls fem-3 mRNA. NOS-1 and NOS-2 also function in the switch, but do not interact directly with FBF. The three C. elegans nanos genes, like Drosophila nanos, are also critical for germ-line survival. We propose that this may have been the primitive function of nanos genes.
Kraemer
B
B
Department of Biochemistry University of Wisconsin-Madison Madison, Wisconsin 53706, USA.
Crittenden
S
S
Gallegos
M
M
Moulder
G
G
Barstead
R
R
Kimble
J
J
Wickens
M
M
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins; D012734:Disorders of Sex Development / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000737:chemistry / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D015801:Helminth Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D019476:Insect Proteins / Q000737:chemistry; D007814:Larva; D008297:Male; D008954:Models, Biological; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology*; D009866:Oogenesis / Q000235:genetics*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013091:Spermatogenesis / Q000235:genetics*; D013094:Spermatozoa / Q000166:cytology*
D029742:Caenorhabditis elegans Proteins; D029721:Drosophila Proteins; D015801:Helminth Proteins; D019476:Insect Proteins; D016601:RNA-Binding Proteins; C109286:fem-3-binding protein, C elegans; C400702:nos-1 protein, C elegans; C400703:nos-2 protein, C elegans; C070574:nos protein, Drosophila