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PubMed2025

Quantitative Real-Time PCR for Circular RNA Detection and Analysis.

In eukaryotes, nearly 2% of the genome represented by the coding proteins. However, emerging evidence suggest more than 75% of the human genome referred to as noncoding part also plays a crucial role in governing major regulatory pathways. Noncoding RNAs can be categorized into several groups, such as microRNAs (miRNAs), small nuclear RNA (snRNAs), small nucleolar RNA (snoRNAs), transfer RNA (tRNA), and circular RNA (circRNAs), which contribute to this regulatory landscape. Circular RNAs (circRNAs) are identified as a new class of regulatory noncoding RNAs with gene regulatory roles by acting as miRNA or RNA binding protein sponges or interacting with proteins. Researchers employ quantitative real-time PCR methods to examine circular RNA expression utilizing divergent primers for identification and quantification.

RNA, Circular↗

PubMed2004

RNA interference: the molecular immune system.

Introduction of double-stranded RNA (dsRNA) into cells expressing a homologous gene triggers RNA interference (RNAi), or RNA-based gene silencing (RBGS). The dsRNA degrades corresponding host mRNA into small interfering RNAs (siRNAs) by a protein complex containing Dicer. siRNAs in turn are incorporated into the RNA-induced silencing complex (RISC) that includes helicase, RecA, and exo- and endo-nucleases as well as other proteins. Following its assembly, the RISC guides the RNA degradation machinery to the target RNAs and cleaves the cognate target RNA in a sequence-specific, siRNA-dependent manner. RNAi has now been documented in a wide variety of organisms, including plants, fungi, flies, worms, and more recently, higher mammals. In eukaryotes, dsRNA directed against a range of viruses (i.e., HIV-1, RSV, HPV, poliovirus and others) and endogenous genes can induce sequence-specific inhibition of gene expression. In invertebrates, RNAi can be efficiently triggered by either long dsRNAs or 21- to 23-nt-long siRNAs. However, in jawed vertebrates, dsRNA longer than 30 bp can induce interferon and thus trigger undesirable side effects instead of initiating RNAi. siRNAs have been shown to act as potent inducers of RNAi in cultured mammalian cells. Many investigators have suggested that siRNAs may have evolved as a normal defense against endogenous and exogenous transposons and retroelements. Through a combination of genetic and biochemical approaches, some of the mechanisms underlying RNAi have been described. Recent data in C. elegans shows that two homologs of siRNAs, microRNAs (miRNAs) and tiny noncoding RNAs (tncRNAs) are endogenously expressed. However, many aspects of RNAi-induced gene silencing, including its origins and the selective pressures which maintain it, remain undefined. Its evolutionary history may pass through the more primitive immune functions of prokaryotes involving restriction enzymes that degrade plasmid DNA molecules that enter bacterial cells. RNAi has evolved further among eukaryotes, in which its wide distribution suggests early origins. RNAi seems to be involved in a variety of regulatory and immune functions that may differ among various kingdoms and phyla. We present here proposed mechanisms by which RBGS protects the host against endogenous and exogenous transposons and retroelements. The potential for therapeutic application of RBGS technology in treating viral infections such as HIV is also discussed.

AIDS Vaccines↗

PubMed2026

The regulatory role of non-coding RNAs in taxane resistance of breast cancer.

Breast cancer remains a major health concern among women, characterized by a high risk and substantial mortality. Chemotherapy is widely employed as a standard treatment modality to eliminate malignant cells and improve patient survival. Nevertheless, recurrence and chemoresistance arising from taxane treatment have emerged as key factors driving the high mortality rates in cancer patients. Non-coding RNAs (ncRNAs), encompassing microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), represent a key functional output of the human genome and, via intricate regulatory networks, influence nearly all facets of cancer biology, including the development of chemoresistance. Importantly, in taxane-resistant breast cancer cells, the identified miRNAs displayed bifunctional roles: some promoted resistance, whereas others enhanced sensitivity. This functional duality is also observed in lncRNAs, highlighting their context‑dependent regulatory roles. Additionally, ncRNAs are enriched in taxane-resistant cells-derived exosomes, where they play a crucial role in spreading taxane resistance and chemotherapy failure through genetic modulation of taxane‑sensitive cells. Notably, targeting ncRNAs via various therapeutic approaches, including herbal compounds and synthetic peptides, has shown hopeful findings in reversing taxane resistance in breast cancer, highlighting a promising avenue for the management of taxane resistance in breast cancer.

Breast cancer↗

PubMedDate not supplied

Identification of new small non-coding RNAs from tobacco and Arabidopsis.

Small non-coding RNAs (ncRNAs) have typically been searched in fully sequenced genomes using one of two approaches-experimental or computational. We developed a mixed method, using both types of information, which has the advantage of applying bio-computing methods to actually expressed sequences. Our method allowed the identification of new small ncRNAs in Arabidopsis thaliana and in the unfinished genome of Nicotiana tabacum. We constructed a N. tabacum cDNA library from small RNAs ranging from 20 to 30 nucleotides (nt). The sequences from 73 unique clones were compared to the A. thaliana genome and to all plant sequences using a pattern-matching approach (program Patbank). Thus, we selected 15 clones from the library corresponding mostly to A. thaliana or N. tabacum non-coding sequences. By Northern blot analyses, we confirmed the presence of most RNA candidates in Arabidopsis and in Nicotiana sylvestris with a size range of 21-100 nt. To gain more insight into the possible genesis of 21-24 nt sequences, stable folding of sRNAs with their flanking regions were predicted with the software MIRFOLD dedicated to the folding of microRNAs (miRNA). Stable hairpins structures were observed for some putative miRNAs.

Arabidopsis↗

PubMed2006

Hepatitis B virus integration, fragile sites, and hepatocarcinogenesis.

Chronic liver disease associated with long term hepatitis B virus (HBV) infection contributes importantly to the development of hepatocellular carcinoma (HCC). A salient feature of these chronic infections is the integration of subgenomic HBV DNA fragments into many different locations within the host DNA, suggesting that integration is random. Although this may promote genetic instability during liver regeneration which accompanies a bout of chronic liver disease, the actual role of integrated HBV DNA in hepatocarcinogenesis is uncertain. Importantly, most integration events retain the HBV open reading frame encoding the HBx antigen (HBxAg), which is the virus contribution to HCC. In addition, many integration events reported in the literature occur near or within fragile sites or other cancer associated regions of the human genome that are prone to instability in tumor development and progression. Genetic instability associated with integration potentially alters the expression of oncogenes, tumor suppressor genes, and microRNAs (miRNAs) that may contribute importantly to tumorigenesis. If so, then selected integration events may alter pathways that are rate limiting in hepatocarcinogenesis, thereby providing targets with diagnostic/prognostic potential and for therapeutic intervention.

Cell Transformation, Neoplastic↗

PubMed2006

Regulation of AUXIN RESPONSE FACTOR3 by TAS3 ta-siRNA affects developmental timing and patterning in Arabidopsis.

MicroRNAs (miRNAs) and trans-acting siRNAs (ta-siRNAs) in plants form through distinct pathways, although they function as negative regulators of mRNA targets by similar mechanisms . Three ta-siRNA gene families (TAS1, TAS2, and TAS3) are known in Arabidopsis thaliana. Biogenesis of TAS3 ta-siRNAs, which target mRNAs encoding several AUXIN RESPONSE FACTORs (including ARF3/ETTIN and ARF4 ) involves miR390-guided processing of primary transcripts, conversion of a precursor to dsRNA through RNA-DEPENDENT RNA POLYMERASE6 (RDR6) activity, and sequential DICER-LIKE4 (DCL4)-mediated cleavage events. We show that the juvenile-to-adult phase transition is normally suppressed by TAS3 ta-siRNAs, in an ARGONAUTE7-dependent manner, through negative regulation of ARF3 mRNA. Expression of a nontargeted ARF3 mutant (ARF3mut) in a wild-type background reproduced the phase-change phenotypes detected in rdr6-15 and dcl4-2 mutants, which lose all ta-siRNAs. Expression of either ARF3 or ARF3mut in rdr6-15 plants, in which both endogenous and transgenic copies of ARF3 were derepressed, resulted in further acceleration of phase change and severe morphological and patterning defects of leaves and floral organs. In light of the functions of ARF3 and ARF4 in organ asymmetry, these data reveal multiple roles for TAS3 ta-siRNA-mediated regulation of ARF genes in developmental timing and patterning.

Arabidopsis↗

PubMed2006

Mismatched siRNAs downregulate mRNAs as a function of target site location.

In mammalian cells, RNA interference can be mediated by synthetic duplex RNAs, termed small interfering RNAs (siRNAs), which assist in cleaving completely complementary mRNA transcripts. MicroRNAs (miRNAs) are endogenous small RNAs that assist in translationally repressing mRNAs with regions of partial complementarity, but may also reduce transcript levels. Since miRNAs predominantly interact with the 3' UTRs of transcripts, we sought to ask if mismatched siRNAs mimicking miRNAs affect cognate mRNA levels as a function of target site location. We find that mismatched siRNAs targeting the 3' UTRs of two endogenous transcripts yield a greater reduction in mRNA levels than those targeting the coding region. Our findings demonstrate the importance of target site location within endogenous mRNAs for small RNAs associated with RNAi.

ATP-Binding Cassette Transporters↗

PubMed2006

Mutants defective in a Mucor circinelloides dicer-like gene are not compromised in siRNA silencing but display developmental defects.

Dicer proteins are ribonuclease III enzymes that process double stranded RNA precursors into small RNAs categorized as small interfering RNAs (siRNAs) or microRNAs (miRNAs), which suppress gene expression through the RNA silencing mechanism. We have isolated a dicer-like gene (dcl-1) of Mucor circinelloides, the first gene of this family to be identified in zygomycetes. The dcl-1 mRNA occurred in multiple forms, including the truncated molecules that result from premature polyadenylation. Null dcl-1 mutants were not impaired as regards transgene-induced gene silencing, since they exhibited the same silencing frequency as the wild-type strain and accumulated the two size classes of siRNA associated with RNA silencing in M. circinelloides. However, dcl-1 mutants showed a reduced growth rate and a hyphal growth alteration, which suggests that the dcl-1 gene has some role in the control of endogenous functions.

Base Sequence↗

PubMed2005

The dialectics of cancer: A theory of the initiation and development of cancer through errors in RNAi.

The recent discoveries of the RNA-mediated interference system in cells could explain all of the known features of human carcinogenesis. A key, novel idea, proposed here, is that the cell has the ability to recognise a mutated protein and/or mRNA. Secondly, the cell can generate its own short interfering RNA (siRNA) using an RNA polymerase to destroy mutated mRNA, even when only a single base pair in the gene has mutated. The anti-sense strand of the short RNA molecule (called sicRNA), targets the mutated mRNA of an oncogene or a tumour suppressor. The resulting double stranded RNA, using the RNA-induced silencing complex in the cytoplasm dices the mutated mRNA. In cancer-prone tissues, during cell mitosis, the sicRNA complex can move into the nucleus to target the mutated gene. The sicRNA, possibly edited by dsRNA-specific adenosine deaminase, converting adenosines to inosines, can be retained in the nucleus, with enhanced destructive capability. The sicRNA triggers the assembly of protein complexes leading to epigenetic modification of the promoter site of the mutant gene, specifically methylation of cytosines. In some instances, instead of methylation, the homologous DNA is degraded, leading to loss of heterozygosity. The factors controlling these two actions are unknown but the result is gene silencing or physical destruction of the mutant gene. The cell survives dependent on the functioning of the single, wild-type allele. An error in RNAi defence occurs when the sicRNA enters the nucleus and targets the sense strand of the wrong DNA. The sicRNA, because of the similarity of its short sequence and relaxed stringency, can target other RNAs, which are being transcribed. This can result in the methylation of the wrong promoter site of a gene or LOH of that region. In the vast majority of these cases, the aberrant hybridisations will have no effect on cell function or apoptosis eliminates non-viable cells. On a rare occasion, a preneoplastic cell is initiated when aberrant hybridisations switches on/off a gene involved in apoptosis, as well as a gene involved in cell proliferation and DNA damage surveillance. Genetic instability results when the sicRNA competes for a repeat sequence in the centromere or telomere, leading to gross chromosomal rearrangements. A malignancy develops when the sicRNAs fortuitously targets a microRNA (miRNA) or activates a transcription factor, resulting in the translation of a large number of new genes, alien to that tissue. This leads to dedifferentiation of the tissue, a resculpting of the histone code, chromosomal rearrangements, along a number of specific pathways, the gain of immortality and the dissemination of a metastatic cancer.

CpG Islands↗

PubMed2005

Emerging from the fog: hypotheses and paradigms in developmental biology--the Society for Developmental Biology 2005 Annual Meeting Report.

The Society for Developmental Biology 64th annual meeting took place by the beautiful San Francisco Bay from July 27th to August 1st, 2005. Organized under the leadership of Judith Kimble (SDB President, U. Wisconsin-Madison), the meeting attracted over one thousand developmental biologists from all over the world. They gathered to present data, exchange ideas and enjoy basking in the warm sun on the piers. Strong themes emerged from the diverse subjects discussed at the meeting, demonstrating exciting trends towards the unifying goal of understanding the progression from a single cell to an adult organism. Cell and Tissue Polarity was a recurring topic at the meeting. Questions like "is there polarity", "how is it achieved" and "how is it linked to stem cell maintenance" were discussed. Post-transcriptional regulation involving protein degradation and microRNA (miRNA) modulation of gene expression was featured in the context of transition between meiosis to mitosis and asymmetries in the embryo. It is apparent that Evolutionary Developmental Biology, once a major driving influence in the early days of the field, continues to enjoy a renaissance as researchers familiar with traditional model organisms are increasingly attracted to the field and as modern genetic and molecular approaches are applied to an increasingly varied assortment of organisms. The attention is beginning to pay off as laboratories are starting to generate significant results shedding light into how developmental programs are altered to generate morphological diversity. In the Satellite Symposium on Plant Development held on July 27th, 2005, the overriding theme was on the identity and maintenance of Stem Cells in Plants. Finally, researchers working on diverse organisms have shown a strong effort to address Developmental Coordination: on the subcellular, cellular and tissue levels. Advanced imaging techniques are combined with traditional genetic methods to scrutinize and compare dynamic processes in four dimensions. This tremendous increase in resolution has facilitated the identification of key signaling mechanisms that embryos utilize to form coordinated body plans. For an exceptional effort in keeping with Society tradition, the 2005 annual meeting also offered opportunities to address broader issues revolving around education and professional development as well as a special session on embryonic stem cell research. Throughout the 5-day meeting, participants found time to honor the contributions of colleagues, exchange career and grant planning strategies, contemplate the big picture and recognize the efforts of young investigators, postdoctoral fellows and students.

Animals↗

PubMed2006

Impact of RNA interference on gene networks.

Small endogenous RNAs such as microRNAs (miRNAs) and small interfering RNAs (siRNAs) have been found to post-transcriptionally control cellular gene networks by targeting complementary mRNAs for translation impairment (miRNA) or destruction (siRNA). We have developed a computational model, coordinated to molecular and biochemical parameters of RNA interference pathways, to provide (semi-) quantitative insight into the molecular events managing siRNA-mediated gene expression silencing in native and synthetic gene networks. Based on mass-conservation principles and kinetic rate laws, we converted biochemical RNA interference pathways into a set of ordinary differential equations that describe the dynamics of siRNA-mediated translation-regulation in mammalian cells. Capitalizing on mechanistic details of synthetic transactivator operation, we wired this model into a transcription control circuitry in which the siRNA and its target mRNA are independently regulated at the transcriptional level. In this context, we studied the impact of siRNA transcription timing on the onset of target gene transcription and production kinetics of target mRNA-encoded proteins. We also simulated the rate of siRNA-induced mRNA depletion and demonstrated that the relative concentrations of interacting siRNAs/mRNAs and the number of siRNA-specific target sites on a transcript modulate (i) the rate of target mRNA disappearance, (ii) the steady-state mRNA levels and (iii) induction dynamics of mRNA-encoded protein production. As our model predictions are consistent with available biochemical parameters, extrapolations may improve our understanding of how complex regulatory gene networks are impacted by small endogenous RNAs.

Gene Expression Regulation↗

PubMed2005

Viral delivery of recombinant short hairpin RNAs.

Recent work demonstrates that RNA interference (RNAi) can coordinate protein expression. Inhibitory RNAs are expressed naturally in cells as microRNAs (miRNAs) or introduced into cells as small interfering RNAs (siRNAs). Both types of small RNAs can be used at the bench to silence mRNA expression. For many researchers, transfection of siRNAs synthesized in vitro or purchased from commercial sources is impractical for the cellular system under study. As an alternative to transfection-based methods, we provide a practical approach to accomplish siRNA-mediated gene silencing through the generation and introduction of recombinant viral vectors expressing short hairpin RNAs (shRNAs). shRNAs are subsequently processed to siRNAs in vivo, leading to efficient, and, in some cases, long-term silencing.

Adenoviridae↗

PubMed2005

Human dicer: purification, properties, and interaction with PAZ PIWI domain proteins.

Dicer is a multidomain ribonuclease that processes double-stranded RNAs (dsRNAs) to 21-nt small interfering RNAs (siRNAs) during RNA interference and excises microRNAs (miRNAs) from precursor hairpins. PAZ and PIWI domain (PPD) proteins, also involved in RNAi and miRNA function, are the best-characterized proteins known to interact with Dicer. PPD proteins are the core constituents of effector complexes, RISCs and miRNPs, mediating siRNA and miRNA function. In this chapter we describe overexpression and purification of recombinant human Dicer, its biochemical properties, and mapping of domains responsible for Dicer-PPD protein interactions.

Amino Acid Sequence↗

PubMed2005

Regulatory networks of the phytohormone abscisic acid.

Structurally similar to retinoic acid (RA), the phytohormone abscisic acid (ABA) controls many developmental and physiological processes via complicated signaling networks that are composed of receptors, secondary messengers, protein kinase/phosphatase cascades, transcription factors, and chromatin-remodeling factors. In addition, ABA signaling is further modulated by mRNA maturation and stability, microRNA (miRNA) levels, nuclear speckling, and protein degradation. This chapter highlights the identified regulators of ABA signaling and reports their homologues in dicotyledonous and monocotyledonous plants.

Abscisic Acid↗

PubMed2006

A novel class of small RNAs bind to MILI protein in mouse testes.

Small RNAs bound to Argonaute proteins recognize partially or fully complementary nucleic acid targets in diverse gene-silencing processes. A subgroup of the Argonaute proteins--known as the 'Piwi family'--is required for germ- and stem-cell development in invertebrates, and two Piwi members--MILI and MIWI--are essential for spermatogenesis in mouse. Here we describe a new class of small RNAs that bind to MILI in mouse male germ cells, where they accumulate at the onset of meiosis. The sequences of the over 1,000 identified unique molecules share a strong preference for a 5' uridine, but otherwise cannot be readily classified into sequence families. Genomic mapping of these small RNAs reveals a limited number of clusters, suggesting that these RNAs are processed from long primary transcripts. The small RNAs are 26-31 nucleotides (nt) in length--clearly distinct from the 21-23 nt of microRNAs (miRNAs) or short interfering RNAs (siRNAs)--and we refer to them as 'Piwi-interacting RNAs' or piRNAs. Orthologous human chromosomal regions also give rise to small RNAs with the characteristics of piRNAs, but the cloned sequences are distinct. The identification of this new class of small RNAs provides an important starting point to determine the molecular function of Piwi proteins in mammalian spermatogenesis.

Animals↗

PubMed2006

Dissecting Arabidopsis thaliana DICER function in small RNA processing, gene silencing and DNA methylation patterning.

Small RNAs have several important biological functions. MicroRNAs (miRNAs) and trans-acting small interfering RNAs (tasiRNAs) regulate mRNA stability and translation, and siRNAs cause post-transcriptional gene silencing of transposons, viruses and transgenes and are important in both the establishment and maintenance of cytosine DNA methylation. Here, we study the role of the four Arabidopsis thaliana DICER-LIKE genes (DCL1-DCL4) in these processes. Sequencing of small RNAs from a dcl2 dcl3 dcl4 triple mutant showed markedly reduced tasiRNA and siRNA production and indicated that DCL1, in addition to its role as the major enzyme for processing miRNAs, has a previously unknown role in the production of small RNAs from endogenous inverted repeats. DCL2, DCL3 and DCL4 showed functional redundancy in siRNA and tasiRNA production and in the establishment and maintenance of DNA methylation. Our studies also suggest that asymmetric DNA methylation can be maintained by pathways that do not require siRNAs.

DNA Methylation↗

PubMed2026

Liquid biopsy for early detection of pancreatic ductal adenocarcinoma.

There is no clinically relevant blood-based assay for the detection of early-stage pancreatic ductal adenocarcinoma (PDAC), a solid malignancy characterized by poor outcomes. Here we developed, validated and tested a blood-based microRNA (miRNA) assay (which included hsa-miR-142-3p, hsa-miR-30c-5p, hsa-miR-335-5p, hsa-miR-340-5p, hsa-miR-200b-3p, hsa-miR-1260b, hsa-miR-145-3p, hsa-miR-145-5p, hsa-miR-429 and hsa-miR-200a-3p) and a composite score, PANXEON (PANcreatic cancer eXosome Early detectiON), that integrates the miRNA signature with carbohydrate antigen 19-9 for the detection of early-stage PDAC. We conducted an international, multicenter, observational, prospective biomarker study that involved 1,785 individuals with and without PDAC from four countries. The miRNA signature achieved an area under the receiver operating characteristic curve of 88.6% in the testing cohort, with a sensitivity of 83.8% for early-stage PDAC, while showing minimal cross-reactivity with other gastrointestinal cancers. In a cohort of 19 individuals, the miRNA signature levels decreased during neoadjuvant chemotherapy and after surgery and increased before disease recurrence. When combined with carbohydrate antigen 19-9 levels, this blood assay demonstrated a sensitivity of 86.8% for stage I-II PDAC, false-positive rates of 3.2% in low-risk controls and 15.6% in high-risk controls in the testing cohort. PANXEON demonstrates potential for detecting high-grade dysplasia in individuals with high-risk pancreatic cysts (64.3%). Collectively, we present a composite biomarker that may complement existing strategies for the detection of early-stage PDAC and warrants further large-scale prospective studies. ClinicalTrials.gov registration: NCT06388967 .

Journal Article↗

PubMed2005

Exploring the functions of RNA interference pathway proteins: some functions are more RISCy than others?

PPD (PAZ Piwi domain) proteins and the Dicer family have been the subjects of intense study over the last 6 years. These proteins have well-established roles in RNAi (RNA interference), a process that relies on siRNAs (small interfering RNAs) or miRNAs (microRNAs) to mediate specificity. The development of techniques for applying RNAi as a laboratory tool and a molecular therapeutic technique has rapidly outpaced our understanding of the biology of this process. However, over the last 2 years, great strides have been made towards elucidating how PPD proteins and Dicer regulate gene-silencing at the pre- and post-transcriptional levels. In addition, evidence is beginning to emerge that suggests that these proteins have additional siRNA-independent roles as cell-cycle regulators. In the present review, we summarize the well-known roles of these two classes of proteins in gene-silencing pathways, as well as explore the evidence for novel roles of PPD and Dicer proteins.

Cell Cycle↗