An RNA-Binding Multimer Specifies Nematode Sperm Fate

Publication date: 26 June 2018
Source:Cell Reports, Volume 23, Issue 13
Author(s): Scott T. Aoki, Douglas F. Porter, Aman Prasad, Marvin Wickens, Craig A. Bingman, Judith Kimble
FOG-3 is a master regulator of sperm fate in Caenorhabditis elegans and homologous to Tob/BTG proteins, which in mammals are monomeric adaptors that recruit enzymes to RNA binding proteins. Here, we determine the FOG-3 crystal structure and in vitro demonstrate that FOG-3 forms dimers that can multimerize. The FOG-3 multimeric structure has a basic surface potential, suggestive of binding nucleic acid. Consistent with that prediction, FOG-3 binds directly to nearly 1,000 RNAs in nematode spermatogenic germ cells. Most binding is to the 3′ UTR, and most targets (94%) are oogenic mRNAs, even though assayed in spermatogenic cells. When tethered to a reporter mRNA, FOG-3 represses its expression. Together these findings elucidate the molecular mechanism of sperm fate specification and reveal the evolution of a protein from monomeric to multimeric form with acquisition of a distinct mode of mRNA repression.

Graphical abstract

Teaser

The mechanism of the sperm or oocyte fate decision has been elusive. Aoki et al. report that nematode FOG-3, a Tob/BTG protein driving sperm fate, has evolved from monomeric to multimeric form with acquisition of a divergent Tob/BTG mechanism for mRNA repression.


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