Dose-Dependent Effects of GLD-2 and GLD-1 on Germline Differentiation and Dedifferentiation in the Absence of PUF-8.

PUMILIO/FBF (PUF) proteins have a conserved function in stem cell regulation.Caenorhabditis elegansPUF-8 protein inhibits the translation of target mRNAs by interacting with PUF binding element (PBE) in the 3 ' untranslated region (3 ' UTR). In this work, anin silicoanalysis has identifiedgld-2[a poly(A) polymerase] as a putative PUF-8 target. Biochemical and reporter analyses showed that PUF-8 specifically binds to a PBE ingld-23 ' UTR and represses a GFP reporter gene carryinggld-23 ' UTR in theC. elegansmitotic germ cells. GLD-2 enhances meiotic entry at least in part by activating GLD-1 (a KH motif-containing RNA-binding protein). Our genetic analyses also demonstrated that heterozygousgld-2(+/-) gld-1(+/-)genes in the absence of PUF-8 are competent for meiotic entry (early differentiation), but haplo-insufficient for the meiotic division (terminal differentiation) of spermatocytes. Indeed, the arrested spermatocytes return to mitotic cells via dedifferentiation, which results in germline tumors. Since these regulators are broadly conserved, we thus suggest that similar molecular mechanisms may control differentiation, dedifferentiation, and tumorigenesis in other organisms, including humans.