RNAa-Mediated Epigenetic Attenuation of The Cell Senescence via Locus Specific Induction of Endogenous SIRT1

SIRT1, a known regulator of cellular senescence, is a therapeutic target for age related disorders and its upregulation is a strategy to improve the cell therapeutic potentials of human mesenchymal stem cell (MSCs). Knockdown of natural antisense transcripts via small activating RNAs (RNAa) is an emerging approach for safe and locus specific gene regulation. We have recently identified a natural antisense transcript at human SIRT1 locus (SIRT1-NAT), the expression of which shows a negative correlation with that of SIRT1. To test the hypothetic upregulation of SIRT1 via knockdown of SIRT1-NAT, in this study we designed a single stranded oligonucleotide (SIRT1-antagoNAT) against the antisense transcript, transfection of which efficiently knocked down the SIRT1-NAT and induced SIRT1 transcription in human MSCs. In addition, activation of SIRT1 transfection via knockdown of SIRT1-NAT in human MSCs enhanced their proliferation and differentiation potentials, reduced senescence associated β-galactosidase activity and reversed the senescence associated molecular alterations. Our findings introduce an RNAa mediated approach for epigenetic induction of endogenous SIRT1 and the consequent attenuation of senescence. Further studies should evaluate the therapeutic potentials of this approach against various age related disorders.

The fate of notch-1 transcript is linked to cell cycle dynamics by activity of a natural antisense transcript

A core imprint of metazoan life is that perturbations of cell cycle are offset by compensatory changes in successive cellular generations. This trait enhances robustness of multicellular growth and requires transmission of signaling cues within a cell lineage. Notably, the identity and mode of activity of transgenerational signals remain largely unknown. Here we report the discovery of a natural antisense transcript encoded in exon 25 of notch-1 locus (nAS25) by which mother cells control the fate of notch-1 transcript in daughter cells to buffer against perturbations of cell cycle. The antisense transcript is transcribed at G1 phase of cell cycle from a bi-directional E2F1-dependent promoter in the mother cell where the titer of nAS25 is calibrated to the length of G1. Transmission of the antisense transcript from mother to daughter cells stabilizes notch-1 sense transcript in G0 phase of daughter cells by masking it from RNA editing and resultant nonsense-mediated degradation. In consequence, nAS25-mediated amplification of notch-1 signaling reprograms G1 phase in daughter cells to compensate for the altered dynamics of the mother cell. The function of nAS25/notch-1 in integrating G1 phase history of the mother cell into that of daughter cells is compatible with the predicted activity of a molecular oscillator, slower than cyclins, that coordinates cell cycle within cell lineage.

Natural Antisense Transcript PEBP1P3 Regulates the RNA Expression, DNA Methylation and Histone Modification of CD45 Gene

The leukocyte common antigen CD45 is a transmembrane phosphatase expressed on all nucleated hemopoietic cells, and the expression levels of its splicing isoforms are closely related to the development and function of lymphocytes. PEBP1P3 is a natural antisense transcript from the opposite strand of CD45 intron 2 and is predicted to be a noncoding RNA. The genotype-tissue expression and quantitative PCR data suggested that PEBP1P3 might be involved in the regulation of expression of CD45 splicing isoforms. To explore the regulatory mechanism of PEBP1P3 in CD45 expression, DNA methylation and histone modification were detected by bisulfate sequencing PCR and chromatin immunoprecipitation assays, respectively. The results showed that after the antisense RNA PEBP1P3 was knocked down by RNA interference, the DNA methylation of CD45 intron 2 was decreased and histone H3K9 and H3K36 trimethylation at the alternative splicing exons of CD45 DNA was increased. Knockdown of PEBP1P3 also increased the binding levels of chromatin conformation organizer CTCF at intron 2 and the alternative splicing exons of CD45. The present results indicate that the natural antisense RNA PEBP1P3 regulated the alternative splicing of CD45 RNA, and that might be correlated with the regulation of histone modification and DNA methylation.

The natural antisense transcript DONE40 derived from the lncRNA ENOD40 locus interacts with SET domain protein ASHR3 during inception of symbiosis in Arachis hypogaea

The lncRNA ENOD40 is required for cortical cell division during root nodule symbiosis (RNS) of legumes, though it is not essential for actinorhizal RNS. Our objective was to understand whether ENOD40 was required for aeschynomenoid nodule formation in Arachis hypogaea. AhENOD40 express from chr5 (AhENOD40-1) and chr15 (AhENOD40-2) during symbiosis, and RNA interference of these transcripts drastically affected nodulation indicating the importance of ENOD40 in A.hypogaea. Furthermore, we demonstrated several distinct characteristics of ENOD40: (i) Natural antisense transcript of ENOD40 was detected from the AhENOD40-1 locus (designated as NAT-AhDONE40). (ii) Both AhENOD40-1 and AhENOD40-2 had two exons, whereas NAT-AhDONE40 was monoexonic. RT-qPCR analysis indicated both sense and antisense transcripts to be present in both cytoplasm and nucleus, and their expression increased with the progress of symbiosis. (iii) RNA Pulldown from whole cell extracts of infected roots at 4DPI indicated NAT-AhDONE40 to interact with the SET (Su(var)3-9, Enhancer-of-zeste and Trithorax) domain containing Ash (Absent Small homeotic disc) family protein AhASHR3 and this interaction was further validated using RNA immunoprecipitation and EMSA. (iv) ChIP assays indicate deposition of ASHR3 specific histone marks H3K36me3 and H3K4me3 in both the ENOD40 loci during the progress of symbiosis. ASHR3 is known for its role in optimizing cell proliferation and reprogramming. Since both ASHR3 and ENOD40 from legumes cluster away from those in actinorhizal plants and other nonlegumes in phylogenetic distance trees, we hypothesize that the interaction of DONE40 with ASHR3 could have evolved for adapting the nodule organogenesis program for legumes.

LADON, a natural antisense transcript of NODAL, promotes metastasis in melanoma by repressing NDRG1

SummaryThe TGFβ family member NODAL, primarily known for its role during embryonic development, has also been associated with tumor progression in a number of cancers. Some of the evidence supporting its involvement in melanoma has appeared contradictory, suggesting that NODAL in this context might rely on a non-canonical mode of signaling. To investigate this possibility we studied how a deletion of NODAL affected cell behavior in a metastatic melanoma cell line. The mutation does prevent melanoma cells from acquiring an invasive behavior. However, this phenotype was found to result not from the absence of NODAL, but from the disabled expression of a natural antisense transcript of NODAL now called LADON. Its expression promotes the mesenchymal to amoeboid transition that is critical to melanoma cells’ invasiveness. Our analyses revealed that the increase in LADON expression necessary to complete this transition is dependent on WNT/β-CATENIN signaling and that its downstream effectors include MYCN and the metastasis suppressor NDRG1, which controls changes in the cytoskeleton. These results identify LADON as a player in the network of interactions governing tumor progression in melanoma, and suggest a similar implication in other cancer types.