piRNA-directed cleavage of meiotic transcripts regulates spermatogenesis

MIWI catalytic activity is required for spermatogenesis, indicating that piRNA-guided cleavage is critical for germ cell development. To identify meiotic piRNA targets, we augmented the mouse piRNA repertoire by introducing a human meiotic piRNA cluster. This triggered a spermatogenesis defect by inappropriately targeting the piRNA machinery to mouse mRNAs essential for germ cell development. Analysis of such de novo targets revealed a signature for pachytene piRNA target recognition. This enabled identification of both transposable elements and meiotically expressed protein-coding genes as targets of native piRNAs. Cleavage of genic targets began at the pachytene stage and resulted in progressive repression through meiosis, driven at least in part via the ping-pong cycle. Our data support the idea that meiotic piRNA populations must be strongly selected to enable successful spermatogenesis, both driving the response away from essential genes and directing the pathway toward mRNA targets that are regulated by small RNAs in meiotic cells.     

An insight into the roles of piRNAs and PIWI proteins in the diagnosis and pathogenesis of oral,esophageal, and gastric cancer

P-Element induced wimpy testis (PIWI)-interacting RNA (piRNA) is a member of the non-coding RNAs family. Four PIWI proteins are found to be expressed in humans. The number of studies focusing on the roles of piRNAs and PIWI proteins in the field of cancer is increasing. Oral, esophageal, and gastric cancers are considered as important causes of death. PIWI proteins and piRNAs are suggested to be involved in the pathogenesis of these diseases. Thus, studying these molecules may be beneficial for finding new therapeutics. Since it is shown that currently used biomarkers for these cancers have low sensitivity and specificity, there is a necessity for identifying novel non-invasive biomarkers which are highly sensitive and specific. This paper will provide an insight into current knowledge about the functions of PIWI proteins and piRNAs in the oral, esophageal, and gastric cancer. We discuss how PIWI proteins and piRNAs can be involved in the pathogenesis of these cancers. Moreover, we review the studies concerning with the roles of PIWI proteins and piRNAs as biomarkers which are used for diagnostic and prognostic purposes.     

Roles for the Yb body components Armitage and Yb in primary piRNA biogenesis in Drosophila

PIWI-interacting RNAs (piRNAs) protect genome integrity from transposons. In Drosophila ovarian somas, primary piRNAs are produced and loaded onto Piwi. Here, we describe roles for the cytoplasmic Yb body components Armitage and Yb in somatic primary piRNA biogenesis. Armitage binds to Piwi and is required for localizing Piwi into Yb bodies. Without Armitage or Yb, Piwi is freed from the piRNAs and does not enter the nucleus. Thus, piRNA loading is required for Piwi nuclear entry. We propose that a functional Piwi-piRNA complex is formed and inspected in Yb bodies before its nuclear entry to exert transposon silencing.     

Combined miRNA profiling and proteomics demonstrates that different miRNAs target a common set of proteins to promote colorectal cancer metastasis

The process of liver colonization in colorectal cancer remains poorly characterized. Here, we addressed the role of microRNA (miRNA ) dysregulation in metastasis. We first compared miRNA expression profiles between colorectal cancer cell lines with different metastatic properties and then identified target proteins of the dysregulated miRNAs to establish their functions and prognostic value. We found that 38 miRNAs were differentially expressed between highly metastatic (KM12SM /SW620 ) and poorly metastatic (KM12C /SW480 ) cancer cell lines. After initial validation, we determined that three miRNAs (miR ‐424‐3p, ?503, and ?1292) were overexpressed in metastatic colorectal cancer cell lines and human samples. Stable transduction of non‐metastatic cells with each of the three miRNAs promoted metastatic properties in culture and increased liver colonization in vivo . Moreover, miR ‐424‐3p and miR ‐1292 were associated with poor prognosis in human patients. A quantitative proteomic analysis of colorectal cancer cells transfected with miR ‐424‐3p, miR ‐503, or miR ‐1292 identified alterations in 149, 129, or 121 proteins, respectively, with an extensive overlap of the target proteins of the three miRNAs . Importantly, down‐regulation of two of these shared target proteins, CKB and UBA2 , increased cell adhesion and proliferation in colorectal cancer cells. The capacity of distinct miRNAs to regulate the same mRNAs boosts the capacity of miRNAs to regulate cancer metastasis and underscores the necessity of targeting multiple miRNAs for effective cancer therapy. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

MIR152, MIR200B, and MIR338, human positional and functional neuroblastoma candidates, are involved in neuroblast differentiation and apoptosis

MicroRNAs (MIRs) perform critical regulatory functions within cell networks, both in physiology as well as in pathology. Through the positional gene candidate approach, we have identified three MIRs (MIR152, MIR200B, and MIR338) that are located in regions frequently altered in neuroblastoma (NB) and target mRNAs encoding proteins involved in cell proliferation, neuroblast differentiation, neuroblast migration, and apoptosis. Expression analysis in NB biopsies and NB cell lines showed that these MIRs are dysregulated. We have characterized a CpG island, close to the gene encoding MIR200B and hypermethylated in NB samples, that explains its negative regulation. Expression of MIR152, MIR200B, and MIR338 is specifically modulated in NB cell lines during differentiation and apoptosis. Functional genomic experiments through enforced expression of MIR200B and knockdown of MIR152 resulted in a significant decrease of the invasion activity of SH-SY5Y cells. Reconstruction of a NB network comprising MIR152, MIR200B, and MIR338 allowed us to confirm their role in the control of NB cell stemness and apoptosis: This suggests that altered regulation of these MIRs could have a role in NB pathogenesis by interfering with the molecular mechanisms, which physiologically control differentiation and death of neuroblasts. Accordingly, they could be considered as new NB biomarkers and potential targets of antagomirs or epigenetic therapies.     

Pimet, the Drosophila homolog of HEN1, mediates 2'-O-methylation of Piwi- interacting RNAs at their 3' ends

Piwi-interacting RNAs (piRNAs) consist of a germline-specific group of small RNAs derived from distinct intergenic loci in the genome. piRNAs function in silencing selfish transposable elements through binding with the PIWI subfamily proteins of Argonautes. Here we show that piRNAs in Drosophila are 2'-O-methylated at their 3' ends. Loss of Pimet (piRNA methyltransferase), the Drosophila homolog of Arabidopsis HEN1 methyltransferase for microRNAs (miRNAs), results in loss of 2'-O-methylation of fly piRNAs. Recombinant Pimet shows single-stranded small RNA methylation activity in vitro and interacts with the PIWI proteins within Pimet mutant ovary. These results show that Pimet mediates piRNA 2'-O-methylation in Drosophila.     

The Role of MicroRNAs in Autoimmune Diseases with Skin Involvement

MicroRNAs (miRNAs) are small non‐coding RNA molecules that negatively modulate gene expression by binding to the 3′ untranslated region (UTR) of target messenger RNAs (mRNAs), which leads to the degradation or translational repression of their target mRNAs. Previous research on miRNAs has revealed a new paradigm of gene regulations and pathways involved in the pathogenesis of autoimmune disorders and malignant diseases. The roles of miRNAs in cellular processes, including cell differentiation, proliferation, apoptosis and immune functions, are not clearly understood. MiRNAs are easily detected in a variety of sources, including tissues, serum and other body fluids, and this make them a good biological sample for pathogenic studies and disease biomarker development. This review encompasses the current understanding of the roles of miRNAs in autoimmunity and the cellular and molecular mechanisms of miRNAs in various autoimmune diseases (AIMDs). Specifically, we focus on the target genes of miRNAs and the biological processes associated with autoimmune diseases with skin involvement, including systemic lupus erythematosus, psoriasis, systemic sclerosis, Behcet's disease and dermatomyositis. In addition, the diagnostic and therapeutic relevance of miRNAs that are involved in autoimmunity are elucidated to provide information for clinical implications.     

白纹伊蚊感染登革病毒后病毒特异性piRNAs分析

目的 筛选并分析白纹伊蚊感染登革病毒后病毒特异性vsRNAs与vpiRNAs.方法 白纹伊蚊羽化后2～4d雌性成蚊显微注射DENV-2病毒NGC株,对照组注射生理盐水.8d后提取样品总RNA,分离小RNA,通过illumina Hiseq 2000测序仪进行测序分析.以SOAP2软件与DENV-2基因组和互补序列进行比对.对病毒特异性的vsRNAs与vpiRNAs的长度、碱基与链偏好性、基因组分布进行分析.结果 对于感染蚊虫,我们共计获得3835个特异的DENV-2来源的vsRNAs,其中395个特异性的vpiRNAs.94.99％ vpiRNAs主要来源于病毒的正链基因组.vpiRNAs在DENV-2基因组上的分布也具有偏向性,最高峰位于病毒非结构蛋白NS5编码区域的3＆#39;末端.第10位碱基具有较强的腺嘌呤偏好性,但第1位碱基不具有尿嘧啶偏好性;也无典型“乒乓”扩增循环的特征.结论 白纹伊蚊感染登革病毒后,体内出现病毒特异性vsRNAs与vpiRNAs,对其鉴定与分析将为在白纹伊蚊抗病毒免疫研究提供理论基础.     

Diversity of the piRNA pathway for nonself silencing: worm-specific piRNA biogenesis factors

The PIWI-interacting RNA (piRNA) pathway protects animal germline cells from transposable elements and other genomic invaders. Although the genome defense function of piRNAs has been well established, the mechanisms of their biogenesis remain poorly understood. In this issue of Genes & Development, three groups identify novel factors required for piRNA biogenesis in Caenorhabditis elegans. These works greatly expand our understanding of the piRNA pathway in worms, highlighting both its shared and its unique properties.     

Up‐regulation of PSF1 promotes the growth of breast cancer cells

PSF1 is a subunit of the GINS complex that functions along with the MCM2‐7 complex and Cdc45 in eukaryotic DNA replication. Although mammalian PSF1 is predominantly expressed in highly proliferating cells and organs, little is known about the roles of PSF1 in mature cells or cancer cells. We found that PSF1 was expressed at relatively high levels in breast tumor cells, but at low levels in normal breast cells. Knockdown of PSF1 expression using small interfering RNA (siRNA) slowed the growth of breast cancer cell lines by delaying DNA replication but did not affect proliferation of normal human mammary epithelial cells. Reduced PSF1 expression also inhibited anchorage‐independent growth in breast cancer cell lines. These results suggest that PSF1 over‐expression is specifically involved in breast cancer cell growth. Therefore, PSF1 inhibition might provide new therapeutic approaches for breast cancer.