GLD-3, a Bicaudal-C Homolog that Inhibits FBF to Control Germline Sex Determination in C. elegans

Abstract

The FBF RNA binding proteins control multiple aspects of C. elegans germline development, including sex determination. FBF promotes the oocyte fate at the expense of spermatogenesis by binding a regulatory element in the fem-3 3'UTR and repressing this sex-determining gene. Here we report the discovery of GLD-3, a Bicaudal-C homolog and cytoplasmic protein that physically interacts with FBF. Using RNAi and a gld-3 deletion mutant, we show that GLD-3 promotes the sperm fate, a sex determination effect opposite to that of FBF. By epistasis analysis, GLD-3 acts upstream of FBF, and, in a yeast three-hybrid assay, GLD-3 interferes specifically with FBF binding to the fem-3 3'UTR. We propose that GLD-3 binds FBF and thereby inhibits its repression of target mRNAs.

A regulatory cytoplasmic poly(A) polymerase in Caenorhabditis elegans

“…GLD-2 has little PAP activity on its own, but is stimulated in vitro by GLD-3. GLD-3 is also a developmental regulator, and belongs to the Bicaudal-C family of RNA binding proteins 5 . We suggest that GLD-2 is the prototype for a class of regulatory cytoplasmic PAPs that are recruited to specific mRNAs by a binding partner, thereby targeting those mRNAs for polyadenylation and increased expression.…”

“…5), was discovered in yeast two-hybrid screens. Specifically, using GLD-2 as 'bait', 2,000,000 transformants 8,9 .…”

“…5, right). GLD-2 harbours the catalytic and central domains; GLD-3 has five consecutive K homology (KH)-related motifs 5 Figure 3 The GLD-2 protein. Polyclonal anti-GLD-2 antibodies were affinity purified.…”

Genetics of germ cell development

“…[57][58][59] GLD-3 and NOS-3 inhibit FBF-1 and FBF-2 function, maintaining the meiotic state once it has been initiated. 60,61 C. elegans hermaphrodites produce male and female gametes sequentially: the first few rounds of meiosis produce SPERMATOCYTES, and the rest of the GSCs then commit to OOCYTE production for the remainder of the animal's life. As a result, the timing of meiotic entry in the C. elegans life cycle is intimately tied to gamete sex determination.…”

Caenorhabditis elegans germ line: A model for stem cell biology

“…3; Kadyk and Kimble, 1998;Hansen et al, 2004a,b). Two of these redundant pathways are defined by the activities of GLD-1, a KH-domain containing RNA-binding protein (Francis et al, 1995) and the GLD-2 cytoplasmic poly-A polymerase protein (Wang et al, 2002) that acts in a complex with GLD-3, a Bicaudal C-related protein Eckmann et al, 2002Eckmann et al, , 2004. The GLD-1 and GLD-2 pathways are not only redundant for meiotic entry, they also interact, forming a complex genetic regulatory network.…”