85 research outputs found
The SUMO ligase Su(var)2-10 controls eu- and heterochromatic gene expression via establishment of H3K9 trimethylation and negative feedback regulation
No full textOriginal gel image
The SUMO ligase Su(var)2-10 links piRNA-guided target recognition to chromatin silencing
No full textOriginal gel and microscopy image
Surface Chemistry of Perovskite Oxynitride Photocatalysts: A Computational Perspective
No full textPerovskite oxynitrides are an established class of photocatalyst materials for water splitting. Previous computational studies have primarily focused on their bulk properties and have drawn relevant conclusions on their light absorption and charge transport properties. The actual catalytic conversions, however, occur on their surfaces and a detailed knowledge of the atomic-scale structure and processes on oxynitride surfaces is indispensable to further improve these materials. In this contribution, we summarize recent progress made in the understanding of perovskite oxynitride surfaces, highlight key processes that set these materials apart from their pure oxide counterparts and discuss challenges and possible future directions for research on oxynitrides
New players on the piRNA field
No full textThe nuclear piRNA pathway safeguards genome integrity in the germline by silencing transposable elements. Three recent studies have identified new players in the mammalian pathway. Two of these, TEX15 and SPOCD1, might provide a link between piRNA-guided complexes that recognize genomic targets and the molecular machinery that induces DNA methylation and transcriptional repression during mouse spermatogenesis
Abundant expression of somatic transposon-derived piRNAs throughout Tribolium castaneum embryogenesis
No full textBackground: Piwi-interacting RNAs (piRNAs) are a class of short (~26-31 nt) non protein-coding RNAs expressed in the metazoan germline. The piRNA pathway in arthropods is best understood in the ovary of Drosophila melanogaster, where it acts to silence active transposable elements (TEs). Maternal loading of piRNAs in oocytes is further required for the inheritance of piRNA-mediated transposon defence. However, our understanding of the diversity, evolution and function of the piRNA complement beyond drosophilids is limited. The red flour beetle, Tribolium castaneum, is an emerging model organism separated from Drosophila by ~350 million years of evolution that displays a number of features ancestral to arthropods, including short germ embryogenesis. Here, we characterize the maternally-deposited and zygotically-expressed small RNA and mRNA complements throughout Tribolium castaneum embryogenesis.Results: We find that beetle oocytes and embryos of all stages are abundant in heterogeneous ~28 nt RNAs. These small RNAs originate from discrete genomic loci enriched in TE sequences and display the molecular signatures of transposon derived piRNAs. In addition to the maternally-loaded primary piRNAs, Tribolium embryos produce secondary piRNAs by the cleavage of zygotically-activated TE transcripts via the ping-pong mechanism. The two Tribolium piRNA pathway effector proteins, TcPiwi/Aub and Tc-Ago3, are also expressed throughout the soma of early embryos.Conclusion: Our results show that the piRNA pathway in Tribolium is not restricted to the germline, but also operates in the embryo and may act to antagonize zygotically activated transposons. Taken together, these data highlight a functional divergence of the piRNA pathway between insect
The histone chaperone CAF-1 safeguards somatic cell identity
No full textCellular differentiation involves profound remodelling of chromatic landscapes, yet the mechanisms by which somatic cell identity is subsequently maintained remain incompletely understood. To further elucidate regulatory pathways that safeguard the somatic state, we performed two comprehensive RNA interference (RNAi) screens targeting chromatin factors during transcription-factor-mediated reprogramming of mouse fibroblasts to induced pluripotent stem cells (iPS cells). Subunits of the chromatin assembly factor-1 (CAF-1) complex, including Chaf1a and Chaf1b, emerged as the most prominent hits from both screens, followed by modulators of lysine sumoylation and heterochromatin maintenance. Optimal modulation of both CAF-1 and transcription factor levels increased reprogramming efficiency by several orders of magnitude and facilitated iPS cell formation in as little as 4 days. Mechanistically, CAF-1 suppression led to a more accessible chromatin structure at enhancer elements early during reprogramming. These changes were accompanied by a decrease in somatic heterochromatin domains, increased binding of Sox2 to pluripotency-specific targets and activation of associated genes. Notably, suppression of CAF-1 also enhanced the direct conversion of B cells into macrophages and fibroblasts into neurons. Together, our findings reveal the histone chaperone CAF-1 to be a novel regulator of somatic cell identity during transcription-factor-induced cell-fate transitions and provide a potential strategy to modulate cellular plasticity in a regenerative setting
MicroRNA evolution, expression, and function during short germband development in Tribolium castaneum
No full textMultiple products from microRNA transcripts
No full textA single transcript sometimes codes for more than one product. In bacteria, and in a few exceptional animal lineages, many genes are organized into operons: clusters of open reading frames that are transcribed together in a single polycistronic transcript. However, polycistronic transcripts are rare in eukaryotes. One notable exception is that of miRNAs (microRNAs), small RNAs that regulate gene expression at the posttranscriptional level. The primary transcripts of miRNAs commonly produce more than one functional product, by at least three different mechanisms. miRNAs are often produced from polycistronic transcripts together with other miRNA precursors. Also, miRNAs frequently derive from protein-coding gene introns. Finally, each miRNA precursor can produce two mature miRNA products. We argue, in the present review, that miRNAs are frequently hosted in transcripts coding for multiple products because new miRNA precursor sequences that arise by chance in transcribed regions are more likely to become functional miRNAs during evolution. © 2013 Biochemical Society
Abundant expression of somatic transposon-derived piRNAs throughout Tribolium castaneum embryogenesis
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