piRNAs initiate transcriptional silencing of spermatogenic genes during C. elegans germline development

Cyclin-dependent kinase (CDK) plays a vital role in proliferation control across eukaryotes. Despite this, how CDK mediates cell cycle and developmental transitions in metazoa is poorly understood. In this paper, we identify orthologues of Sld2, a CDK target that is important for DNA replication in yeast, and characterize SLD-2 in the nematode worm Caenorhabditis elegans. We demonstrate that SLD-2 is required for replication initiation and the nuclear retention of a critical component of the replicative helicase CDC-45 in embryos. SLD-2 is a CDK target in vivo, and phosphorylation regulates the interaction with another replication factor, MUS-101. By mutation of the CDK sites in sld-2, we show that CDK phosphorylation of SLD-2 is essential in C. elegans. Finally, using a phosphomimicking sld-2 mutant, we demonstrate that timely CDK phosphorylation of SLD-2 is an important control mechanism to allow normal proliferation in the germline. These results determine an essential function of CDK in metazoa and identify a developmental role for regulated SLD-2 phosphorylation.

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Integrator terminates promoter-proximal Pol II to generate C. elegans piRNA precursors

10.1101/2020.05.01.072298 ◽

2020 ◽

Author(s):

Toni Beltran ◽

Elena Pahita ◽

Subhanita Ghosh ◽

Boris Lenhard ◽

Peter Sarkies

Keyword(s):

Catalytic Activity ◽

Rna Polymerase ◽

Rna Polymerase Ii ◽

Transcription Termination ◽

List Type ◽

Germline Development ◽

Pol Ii ◽

C Elegans

AbstractPiwi-interacting RNAs (piRNAs) play key roles in germline development and genome defence in metazoans. In C. elegans, piRNAs are transcribed from >15000 discrete genomic loci by RNA polymerase II, resulting in 28 nt short-capped piRNA precursors. Here we investigate transcription termination at piRNA loci. We show that the Integrator complex, which terminates snRNA transcription, is recruited to piRNA loci. We show that the catalytic activity of Integrator cleaves nascent capped piRNA precursors associated with promoter-proximal Pol II, resulting in termination of transcription. Loss of Integrator activity, however, does not result in transcriptional readthrough at the majority of piRNA loci. Our results draw new parallels between snRNA and piRNA biogenesis in nematodes, and provide evidence of a role for the Integrator complex as a terminator of promoter-proximal RNA polymerase II.Highlights- Integrator localises to sites of piRNA biogenesis in nematodes- Integrator cleaves nascent RNAs associated with promoter-proximal Pol II at piRNA loci to release short capped piRNA precursors from chromatin- Repression of Pol II elongation at the majority of piRNA loci is independent of Integrator

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mRNA localization is linked to translation regulation in the Caenorhabditis elegans germ lineage

10.1101/2020.01.09.900498 ◽

2020 ◽

Cited By ~ 2

Author(s):

Dylan M. Parker ◽

Lindsay P. Winkenbach ◽

Samuel P. Boyson ◽

Matthew N. Saxton ◽

Camryn Daidone ◽

...

Keyword(s):

Caenorhabditis Elegans ◽

Rna Binding ◽

Rna Binding Proteins ◽

Regulatory Control ◽

Translational Repression ◽

Translation Regulation ◽

Germline Development ◽

P Granules ◽

C Elegans ◽

Early Embryos

AbstractCaenorhabditis elegans early embryos generate cell-specific transcriptomes despite lacking active transcription. This presents an opportunity to study mechanisms of post-transcriptional regulatory control. In seeking the mechanisms behind this patterning, we discovered that some cell-specific mRNAs accumulate non-homogenously within cells, localizing to membranes, P granules (associated with progenitor germ cells in the P lineage), and P-bodies (associated with RNA processing). Transcripts differed in their dependence on 3’UTRs and RNA Binding Proteins, suggesting diverse regulatory mechanisms. Notably, we found strong but imperfect correlations between low translational status and P granule localization within the progenitor germ lineage. By uncoupling these, we untangled a long-standing question: Are mRNAs directed to P granules for translational repression or do they accumulate there as a downstream step? We found translational repression preceded P granule localization and could occur independent of it. Further, disruption of translation was sufficient to send homogenously distributed mRNAs to P granules. Overall, we show transcripts important for germline development are directed to P granules by translational repression, and this, in turn, directs their accumulation in the progenitor germ lineage where their repression can ultimately be relieved.SummaryMaternally loaded mRNAs localize non-homogeneously within C. elegans early embryos correlating with their translational status and lineage-specific fates.

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A single histone H1 isoform (H1.1) is essential for chromatin silencing and germline development in Caenorhabditis elegans

Development ◽

10.1242/dev.128.7.1069 ◽

2001 ◽

Vol 128 (7) ◽

pp. 1069-1080 ◽

Cited By ~ 1

Author(s):

M.A. Jedrusik ◽

E. Schulze

Keyword(s):

Caenorhabditis Elegans ◽

Gene Family ◽

Molecular Mechanisms ◽

Histone H1 ◽

Specific Aspect ◽

Polycomb Group ◽

Germline Development ◽

C Elegans ◽

Proliferation And Differentiation ◽

Germline Proliferation

In remarkable contrast to somatic cells, the germline of the nematode Caenorhabditis elegans efficiently silences transgenic DNA. The molecular mechanisms responsible for this have been shown to implicate chromatin proteins encoded by the mes genes (Kelly, W. G. and Fire, A. (1998) Development 125, 2451–2456), of which two are the C. elegans homologs of Polycomb Group gene transcriptional repressors. We have analyzed the contribution of the histone H1 gene family to this specific aspect of germ cells in C. elegans. We show with isotype-specific double stranded RNA-mediated interference (RNAi) that a single member of this gene family (H1.1) is essential for the repression of a silenced reporter-transgene in the germline of hermaphrodites and males, whereas no change is found in the somatic expression of this reporter. Additionally, RNA-mediated interference with H1.1 gene expression can cause a phenotype with severe affection of germline proliferation and differentiation in the hermaphrodite, and even sterility (5%-11% penetrance). These and further features observed in histone H1.1 RNAi experiments are also characteristic of the mes phenotype (Garvin, C., Holdeman, R. and Strome, S. (1998) Genetics 148, 167–185), which is believed to result from the desilencing of genes required for somatic differentiation in the germline. Our observations therefore support this interpretation of the mes phenotype and they identify a single histone H1 isoform (H1.1) as a new component specifically involved in chromatin silencing in the germline of C. elegans.

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The Polycomb group in Caenorhabditis elegans and maternal control of germline development

Development ◽

10.1242/dev.125.13.2469 ◽

1998 ◽

Vol 125 (13) ◽

pp. 2469-2478 ◽

Cited By ~ 7

Author(s):

I. Korf ◽

Y. Fan ◽

S. Strome

Keyword(s):

Gene Expression ◽

Caenorhabditis Elegans ◽

Polycomb Group ◽

Polycomb Group Proteins ◽

Polycomb Group Protein ◽

Maternal Control ◽

Germline Development ◽

C Elegans ◽

Polycomb Group Genes ◽

Group Protein

Four Caenorhabditis elegans genes, mes-2, mes-3, mes-4 and mes-6, are essential for normal proliferation and viability of the germline. Mutations in these genes cause a maternal-effect sterile (i.e. mes) or grandchildless phenotype. We report that the mes-6 gene is in an unusual operon, the second example of this type of operon in C. elegans, and encodes the nematode homolog of Extra sex combs, a WD-40 protein in the Polycomb group in Drosophila. mes-2 encodes another Polycomb group protein (see paper by Holdeman, R., Nehrt, S. and Strome, S. (1998). Development 125, 2457–2467). Consistent with the known role of Polycomb group proteins in regulating gene expression, MES-6 is a nuclear protein. It is enriched in the germline of larvae and adults and is present in all nuclei of early embryos. Molecular epistasis results predict that the MES proteins, like Polycomb group proteins in Drosophila, function as a complex to regulate gene expression. Database searches reveal that there are considerably fewer Polycomb group genes in C. elegans than in Drosophila or vertebrates, and our studies suggest that their primary function is in controlling gene expression in the germline and ensuring the survival and proliferation of that tissue.

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Structures of mammalian GLD-2 proteins reveal molecular basis of their functional diversity in mRNA and microRNA processing

Nucleic Acids Research ◽

10.1093/nar/gkaa578 ◽

2020 ◽

Vol 48 (15) ◽

pp. 8782-8795

Author(s):

Xiao-Yan Ma ◽

Hong Zhang ◽

Jian-Xiong Feng ◽

Jia-Li Hu ◽

Bing Yu ◽

...

Keyword(s):

Structural Basis ◽

Germline Development ◽

C Elegans ◽

Rna Transcripts ◽

Microrna Processing ◽

Specific Mrnas ◽

The Difference ◽

The Stability ◽

Β Sheet ◽

Positively Charged

Abstract The stability and processing of cellular RNA transcripts are efficiently controlled via non-templated addition of single or multiple nucleotides, which is catalyzed by various nucleotidyltransferases including poly(A) polymerases (PAPs). Germline development defective 2 (GLD-2) is among the first reported cytoplasmic non-canonical PAPs that promotes the translation of germline-specific mRNAs by extending their short poly(A) tails in metazoan, such as Caenorhabditis elegans and Xenopus. On the other hand, the function of mammalian GLD-2 seems more diverse, which includes monoadenylation of certain microRNAs. To understand the structural basis that underlies the difference between mammalian and non-mammalian GLD-2 proteins, we determine crystal structures of two rodent GLD-2s. Different from C. elegans GLD-2, mammalian GLD-2 is an intrinsically robust PAP with an extensively positively charged surface. Rodent and C. elegans GLD-2s have a topological difference in the β-sheet region of the central domain. Whereas C. elegans GLD-2 prefers adenosine-rich RNA substrates, mammalian GLD-2 can work on RNA oligos with various sequences. Coincident with its activity on microRNAs, mammalian GLD-2 structurally resembles the mRNA and miRNA processor terminal uridylyltransferase 7 (TUT7). Our study reveals how GLD-2 structurally evolves to a more versatile nucleotidyltransferase, and provides important clues in understanding its biological function in mammals.

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