Biology subjects

Mourelatos, Z.

Publications and source records attributed to Mourelatos, Z..

3 recordsLinked to original sources

bioRxiv2024

MIWI arginines orchestrate generation of functional pachytene piRNAs and spermiogenesis

N-terminal arginine (NTR) methylation is a conserved feature of PIWI proteins, which are central components of the PIWI-interacting RNA (piRNA) pathway. The significance and precise function of PIWI NTR methylation in mammals remains unknown. In mice, PIWI NTRs bind Tudor domain containing proteins (TDRDs) that have essential roles in piRNA biogenesis and the formation of the chromatoid body. Using mouse MIWI (PIWIL1) as paradigm, we demonstrate that the NTRs are essential for spermatogenesis through the regulation of transposons and gene expression. Surprisingly, the loss of TDRD5 and TDRKH interaction with MIWI results in defective piRNA amplification, rather than an expected failure of piRNA biogenesis. We find that piRNA amplification is necessary for both transposon control and for sustaining levels of select, nonconserved, pachytene piRNAs that target specific mRNAs required for spermatogenesis. Our findings support the notion that the vast majority of pachytene piRNAs are dispensable, acting as autonomous genetic elements that rely for propagation on MIWI piRNA amplification. MIWI-NTRs also mediate interactions with TDRD6 that are necessary for chromatoid body compaction. Furthermore, MIWI-NTRs promote stabilization of spermiogenic transcripts that drive nuclear compaction, which is essential for sperm formation. In summary, the NTRs underpin the diversification of MIWI protein function. Key pointsO_LIMIWI-NTRs coordinate interactions with TDRDs required for piRNA biogenesis to sustain piRNA amplification C_LIO_LIMIWI-NTRs are necessary for both transposon control and for sustaining levels of select pachytene piRNAs that target specific mRNAs required for spermiogenesis C_LIO_LIMIWI-NTRs mediate interactions with TDRD6 to compact the Chromatoid Body C_LIO_LIMIWI-NTRs underlie stabilization of spermiogenic transcripts that drive nuclear compaction, which is essential for sperm formation C_LI

molecular biology↗

bioRxiv2022

The MOV10 RNA helicase is a dosage-dependent host restriction factor for LINE1 retrotransposition in mice

Transposable elements constitute nearly half of the mammalian genome and play important roles in genome evolution. While a multitude of both transcriptional and post-transcriptional mechanisms exist to silence transposable elements, control of transposition in vivo remains poorly understood. MOV10, an RNA helicase, is a potent inhibitor of mobilization of retrotransposons and retroviruses in cell culture assays. Here we report that MOV10 restricts LINE1 retrotransposition in mice. Although MOV10 is broadly expressed, its loss causes only incomplete penetrance of embryonic lethality, and the surviving MOV10-deficient mice are healthy and fertile. Biochemically, MOV10 forms a complex with UPF1, a key component of the nonsense-mediated mRNA decay pathway, and primarily binds to the 3UTR of somatically expressed transcripts in testis. Consequently, loss of MOV10 results in an altered transcriptome and a modest upregulation of two LINE1 families in testis. Analyses using a LINE1 reporter transgene reveal that loss of MOV10 leads to increased LINE1 retrotransposition in somatic and reproductive tissues from both embryos and adult mice. Moreover, the degree of LINE1 retrotransposition inhibition is dependent on the Mov10 gene dosage. Furthermore, MOV10 deficiency reduces reproductive fitness over successive generations. Our findings demonstrate that MOV10 attenuates LINE1 retrotransposition in a dosage-dependent manner in mice. Author summaryTransposable elements (TEs), including L1 and SINEs, are abundant in the genome and play important roles in evolution, development, and diseases. While TEs propagate in individuals and across generations, the host organism needs to suppress them, resulting in an ongoing arms race between TEs and the host genome. L1, a retrotransposon, accounts for about 17% of the mammalian genome. L1 encodes two proteins, which bind to the L1 transcript to form L1 ribonucleoprotein particles. L1 proliferates in the genome via retrotransposition. A multitude of transcriptional and post-transcriptional mechanisms exist to suppress TEs, however, retrotransposition of TEs remains poorly understood. L1 ribonucleoprotein particles are associated with a large number of host proteins, one of which is the MOV10 RNA helicase. MOV10 exhibits anti-viral activities against retroviruses such as HIV-1. In cultured cells, MOV10 is a potent inhibitor of retrotransposition of L1, SINEs, and IAP. Although MOV10 is expressed in a broad range of tissues, loss of MOV10 causes only incomplete penetrance of embryonic lethality. The viable MOV10-deficient mice are grossly normal and fertile. Importantly, analyses using a L1 transgene reporter reveal that MOV10 inhibits L1 retrotransposition in both somatic tissues and reproductive tissues in a gene dosage-dependent manner. Therefore, MOV10 functions as a host restriction factor for L1 and possibly other transposable elements in vivo.

developmental biology↗

bioRxiv2018

Isolation and sequencing of AGO-bound RNAs reveals characteristics of mammalian stem-loop processing in vivo

MicroRNA precursors (pre-miRNAs) are short hairpin RNAs that are rapidly processed into mature microRNAs (miRNAs) in the cytoplasm. Due to their low abundance in cells, sequencing-based studies of pre-miRNAs have been limited. We successfully enriched for and deep sequenced pre-miRNAs in human cells by capturing these RNAs during their interaction with Argonaute (AGO) proteins. Using this approach, we detected > 350 pre-miRNAs in human cells and > 250 pre-miRNAs in a reanalysis of a similar study in mouse cells. We uncovered widespread trimming and non-templated additions to the 3 ends of pre- and mature miRNAs. Additionally, we created an index for microRNA precursor processing efficiency. This analysis revealed a subset of pre-miRNAs that produce low levels of mature miRNAs despite abundant precursors, including an annotated miRNA in the 5 UTR of the DiGeorge syndrome critical region 8 mRNA transcript. This led us to search for AGO-associated stem-loops originating from other mRNA species, which identified hundreds of putative pre-miRNAs derived from human and mouse mRNAs. In summary, we provide a wealth of information on mammalian pre-miRNAs, and identify novel microRNA and microRNA-like elements localized in mRNAs.

molecular biology↗