Erdmann, E. A. | bioRxiv Science

bioRxiv2023

A high-throughput screen identifies RNA binding proteins that affect fertility in Caenorhabditis elegans and reveals a functional relationship between ADR-2 and SQD-1

RNA binding proteins play essential roles in coordinating germline gene expression and development in all organisms. Here, we report that loss of ADR-2, a member of the Adenosine DeAminase acting on RNA (ADAR) family of RNA binding proteins and the sole adenosine-to-inosine RNA editing enzyme in C. elegans, can improve fertility in multiple genetic backgrounds. First, we show that loss of RNA editing by ADR-2 restores normal embryo production to subfertile animals that transgenically express a vitellogenin (yolk protein) fusion to green fluorescent protein. Using this phenotype, a high-throughput screen was designed to identify RNA binding proteins that when depleted yield synthetic phenotypes with loss of adr-2. The screen uncovered a genetic interaction between ADR-2 and SQD-1, a member of the heterogenous nuclear ribonucleoprotein (hnRNP) family of RNA binding proteins. Microscopy, reproductive assays, and high-throughput sequencing reveal that sqd-1 is essential for the onset of oogenesis and oogenic gene expression in young adult animals, and that loss of adr-2 can counteract the effects of loss of sqd-1 on gene expression and rescue the switch from spermatogenesis to oogenesis. Together, these data demonstrate that ADR-2 can contribute to the suppression of fertility and suggest novel roles for both RNA editing-dependent and independent mechanisms in regulating embryogenesis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/565157v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@14a3449org.highwire.dtl.DTLVardef@aead7dorg.highwire.dtl.DTLVardef@1fff947org.highwire.dtl.DTLVardef@46d487_HPS_FORMAT_FIGEXP M_FIG Graphical AbstractFigure created with BioRender. C_FIG Article SummaryThe molecular information that controls early development is RNA. Interactions between RNA and RNA binding proteins (RBPs) are critical for successful reproduction across species. In this study, we uncovered two roles for the RBP ADR-2 in regulating reproduction. First, we demonstrate that the RNA editing activity of ADR-2 regulates fertility. Next, we screened over 250 other RBPs revealed a genetic interaction between ADR-2 and SQD-1. Further analysis revealed that sqd-1 is essential for the onset of oogenesis, and an editing-independent function of ADR-2 influences proper germline gene expression and oocyte fate in these animals.

genetics↗

bioRxiv2023

ADBP-1 regulates ADR-2 nuclear localization to control editing substrate selection

Adenosine-to-inosine (A-to-I) RNA editing, catalyzed by ADAR enzymes, is a prevalent and conserved RNA modification. While A-to-I RNA editing is essential in mammals, in Caenorhabditis elegans, it is not, making them invaluable for RNA editing research. In C. elegans, ADR-2 is the sole catalytic A-to-I editing enzyme, and ADR-1 is an RNA editing regulator. ADAR localization is well-studied in humans but not well-established in C. elegans. In this study, we examine the cellular and tissue-specific localization of ADR-2. We show that while ADR-2 is present in most cells in the embryo, at later developmental stages, its expression is both tissue- and cell-type-specific. Additionally, both ADARs are mainly in the nucleus. ADR-2 is adjacent to the chromosomes during the cell cycle. We show that the nuclear localization of endogenous ADR-2 depends on ADBP-1, not ADR-1. In adbp-1 mutant worms, ADR-2 is mislocalized, while ADR-1 is not, leading to decreased editing levels and de-novo editing, mostly in exons, suggesting that ADR-2 is also functional in the cytoplasm. Besides, mutated ADBP-1 affects gene expression. Furthermore, we show that ADR-2 targets adenosines with different surrounding nucleotides in exons and introns. Our findings indicate that ADR-2 cellular localization is highly regulated and affects its function.

cell biology↗