NANOS-3 and FBF proteins physically interact to control the sperm-oocyte switch in Caenorhabditis elegans

Curr Biol. 1999 Sep 23;9(18):1009-18. doi: 10.1016/s0960-9822(99)80449-7.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Caenorhabditis elegans / embryology
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / growth & development
  • Caenorhabditis elegans / physiology*
  • Caenorhabditis elegans Proteins*
  • Disorders of Sex Development / genetics
  • Disorders of Sex Development / metabolism*
  • Drosophila Proteins*
  • Drosophila melanogaster / chemistry
  • Drosophila melanogaster / genetics
  • Gene Expression Regulation, Developmental*
  • Helminth Proteins / genetics
  • Helminth Proteins / metabolism*
  • Helminth Proteins / physiology
  • Insect Proteins / chemistry
  • Larva
  • Male
  • Models, Biological
  • Molecular Sequence Data
  • Oocytes / cytology*
  • Oogenesis / genetics*
  • Protein Binding
  • Protein Structure, Tertiary
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Species Specificity
  • Spermatogenesis / genetics*
  • Spermatozoa / cytology*


  • Caenorhabditis elegans Proteins
  • Drosophila Proteins
  • Helminth Proteins
  • Insect Proteins
  • RNA-Binding Proteins
  • fem-3-binding protein, C elegans
  • nos-1 protein, C elegans
  • nos-2 protein, C elegans
  • nos protein, Drosophila