Biology subjects

Schreier, J.

Publications and source records attributed to Schreier, J..

4 recordsLinked to original sources

bioRxiv2020

A membrane-associated condensate drives paternal epigenetic inheritance in C. elegans

Transgenerational epigenetic inheritance (TEI) describes the transmission of gene-regulatory information across generations without altering DNA sequences, and allows priming of offspring towards transposable elements (TEs) and changing environmental conditions. One important mechanism that acts in TEI is based on small non-coding RNAs. Whereas factors for maternal inheritance of small RNAs have been identified, paternal inheritance is poorly understood, as much of the cellular content is extruded during spermatogenesis. We identify a phase separation-based mechanism, driven by the protein PEI-1, which is characterized by a BTB-BACK domain and an intrinsically disordered region (IDR). PEI-1 specifically secures the Argonaute protein WAGO-3 within maturing sperm in C. elegans. Localization of PEI granules in mature sperm is coupled, via S-palmitoylation, to myosin-driven transport of membranous organelles. pei-1-like genes are also found in human and often expressed in testis, suggesting that the here identified mechanism may be broadly conserved.

cell biology↗

bioRxiv2020

Protease-mediated processing of Argonaute proteins controls small RNA association

Small RNA pathways defend the germlines of animals against selfish genetic elements and help to maintain genomic integrity. At the same time, their activity needs to be well-controlled to prevent silencing of self genes. Here, we reveal a proteolytic mechanism that controls endogenous small interfering (22G) RNA activity in the Caenorhabditis elegans germline to protect genome integrity and maintain fertility. We find that WAGO-1 and WAGO-3 Argonaute (Ago) proteins are matured through proteolytic processing of their unusually proline-rich N-termini. In the absence of DPF-3, a P-granule-localized N-terminal dipeptidase orthologous to mammalian DPP8/9, processing fails, causing a change of identity of 22G RNAs bound to these WAGO proteins. Desilencing of repeat- and transposon-derived transcripts, DNA damage and acute sterility ensue. These phenotypes are recapitulated when WAGO-1 and WAGO-3 are rendered resistant to DFP-3-mediated processing, identifying them as critical substrates of DPF-3. We conclude that N-terminal processing of Ago proteins regulates their activity and promotes discrimination of self from non-self by ensuring association with the proper complement of small RNAs. Graphical Abstract: The role of DPF-3 in the fertility of the animals O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY In wild type animals, the WAGO-1 and WAGO-3 Argonaute proteins are produced as immature pro-proteins with N-termini (N) that are unusually rich in prolines (P). N-terminal processing by DPF-3 is required for loading of the proper small RNA cargo and stabilization of WAGO-3. Accordingly, loss of this processing activity causes desilencing of transposable elements (TE), cell death and sterility.

molecular biology↗

bioRxiv2020

The double-stranded DNA-binding proteins TEBP-1 and TEBP-2 form a telomeric complex with POT-1

Telomeres are bound by dedicated protein complexes, like shelterin in mammals, which protect telomeres from DNA damage. In the nematode Caenorhabditis elegans, a comprehensive understanding of the proteins interacting with the telomere sequence is lacking. Here, we harnessed a quantitative proteomics approach to screen for proteins binding to C. elegans telomeres, and identified TEBP-1 and TEBP-2, two paralogs that associate to telomeres in vitro and in vivo. TEBP-1 and TEBP-2 are expressed in the germline and during embryogenesis. tebp-1 and tebp-2 mutants display strikingly distinct phenotypes: tebp-1 mutants have longer telomeres than wild-type animals, while tebp-2 mutants display shorter telomeres and a mortal germline, a phenotype characterized by transgenerational germline deterioration. Notably, tebp-1; tebp-2 double mutant animals have synthetic sterility, with germlines showing signs of severe mitotic and meiotic arrest. TEBP-1 and TEBP-2 form a telomeric complex with the known single-stranded telomere-binding proteins POT-1, POT-2, and MRT-1. Furthermore, we find that POT-1 bridges the double- stranded binders TEBP-1 and TEBP-2, with the single-stranded binders POT-2 and MRT-1. These results describe the first telomere-binding complex in C. elegans, with TEBP-1 and TEBP-2, two double-stranded telomere binders required for fertility and that mediate opposite telomere dynamics.

cell biology↗

bioRxiv2020

The IDR-containing protein PID-2 affects Z granules and is required for piRNA-induced silencing in the embryo

In Caenorhabditis elegans, the piRNA (21U RNA) pathway is required to establish proper gene regulation and an immortal germline. To achieve this, PRG-1-bound 21U RNAs trigger silencing mechanisms mediated by RNA-dependent RNA polymerase (RdRP)-synthetized 22G RNAs. This silencing can become PRG-1-independent, and heritable over many generations. This state is named RNAe. It is unknown how and when RNAe is established, and how it is maintained. We show that maternally provided 21U RNAs can be sufficient to trigger RNAe in embryos. Additionally, we identify the IDR-containing protein PID-2, as a factor required to establish and maintain RNAe. PID-2 interacts with two novel, partially redundant, eTudor domain proteins, PID-4 and PID-5. Additionally, PID-5 has a domain related to the X-prolyl aminopeptidase protein APP-1, and binds APP-1, implicating N-terminal proteolysis in RNAe. All three proteins are required for germline immortality, localize to perinuclear foci, affect Z granules, and are required for balancing of 22G RNA populations. Overall, our study identifies three new proteins with crucial functions in the C. elegans small RNA silencing network.

molecular biology↗