Neuronal function of the mRNA decapping complex determines survival of Caenorhabditis elegans at high temperature through temporal regulation of heterochronic gene expression

Selective Destabilization of Transcripts by mRNA Decapping Regulates Oocyte Maturation and Innate Immunity Gene Expression during Ageing in C. elegans

Removal of the 5' cap structure of RNAs (termed decapping) is a pivotal event in the life of cytoplasmic mRNAs mainly catalyzed by a conserved holoenzyme, composed of the catalytic subunit DCP2 and its essential cofactor DCP1. While decapping was initially considered merely a step in the general 5'-3' mRNA decay, recent data suggest a great degree of selectivity that plays an active role in the post-transcriptional control of gene expression, and regulates multiple biological functions. Studies in Caenorhabditis elegans have shown that old age is accompanied by the accumulation of decapping factors in cytoplasmic RNA granules, and loss of decapping activity shortens the lifespan. However, the link between decapping and ageing remains elusive. Here, we present a comparative microarray study that was aimed to uncover the differences in the transcriptome of mid-aged dcap-1/DCP1 mutant and wild-type nematodes. Our data indicate that DCAP-1 mediates the silencing of spermatogenic genes during late oogenesis, and suppresses the aberrant uprise of immunity gene expression during ageing. The latter is achieved by destabilizing the mRNA that encodes the transcription factor PQM-1 and impairing its nuclear translocation. Failure to exert decapping-mediated control on PQM-1 has a negative impact on the lifespan, but mitigates the toxic effects of polyglutamine expression that are involved in human disease.

Biological implications of decapping: beyond bulk mRNA decay

It is well established that mRNA steady-state levels do not directly correlate with transcription rate. This is attributed to the multiple post-transcriptional mechanisms, which control both mRNA turnover and translation within eukaryotic cells. One such mechanism is the removal of the 5' end cap structure of RNAs (decapping). This 5' cap plays a fundamental role in cellular functions related to mRNA processing, transport, translation, quality control, and decay, while its chemical modifications influence the fate of cytoplasmic mRNAs. Decapping is a highly controlled process, performed by multiple decapping enzymes, and regulated by complex cellular networks. In this review, we provide an updated synopsis of 5' end modifications and functions, and give an overview of mRNA decapping enzymes, presenting their enzymatic properties. Focusing on DCP2 decapping enzyme, a major component on the 5'-3' mRNA decay pathway, we describe cis-elements and trans-acting factors that affect its activity, substrate specificity, and cellular localization. Finally, we discuss current knowledge on the biological functions of mRNA decapping and decay factors, highlighting the major questions that remain to be addressed.

mRNA decapping is an evolutionarily conserved modulator of neuroendocrine signaling that controls development and ageing

Eukaryotic 5'-3' mRNA decay plays important roles during development and in response to stress, regulating gene expression post-transcriptionally. In Caenorhabditis elegans, deficiency of DCAP-1/DCP1, the essential co-factor of the major cytoplasmic mRNA decapping enzyme, impacts normal development, stress survival and ageing. Here, we show that overexpression of dcap-1 in neurons of worms is sufficient to increase lifespan through the function of the insulin/IGF-like signaling and its effector DAF-16/FOXO transcription factor. Neuronal DCAP-1 affects basal levels of INS-7, an ageing-related insulin-like peptide, which acts in the intestine to determine lifespan. Short-lived dcap-1 mutants exhibit a neurosecretion-dependent upregulation of intestinal ins-7 transcription, and diminished nuclear localization of DAF-16/FOXO. Moreover, neuronal overexpression of DCP1 in Drosophila melanogaster confers longevity in adults, while neuronal DCP1 deficiency shortens lifespan and affects wing morphogenesis, cell non-autonomously. Our genetic analysis in two model-organisms suggests a critical and conserved function of DCAP-1/DCP1 in developmental events and lifespan modulation.

Relationship between single nucleotide polymorphisms in the 3'UTR of amyloid precursor protein and risk of Alzheimer's disease and its mechanism

Background and objective: Deregulation of the expression of amyloid precursor protein (APP) can lead to the development of Alzheimer's disease (AD). Recent studies have shown that many single nucleotide polymorphisms (SNPs) in the 3' untranslated region (UTR) of APP are associated with the development of AD. Since microRNAs (miRNAs) are involved in the regulation of APP expression, we believe that the APP 3'UTR polymorphism may affect the regulation of APP expression in miRNAs. Results: The levels of miR-101-3p, miR-153-3p, miR-144-3p, miR-381-3p, and miR-383-5p in plasma of patients with AD were significantly lower than those in the control group. The APP-534G/A site A allele was a protective factor for AD risk (adjusted odds ratio (OR) = 0.700, 95% confidence interval (95% CI): 0.573-0.840, P<0.001). The APP-369C/G site variation was not associated with AD risk. The APP-118C/A site A allele was a protective factor for AD (adjusted OR = 0.762, 95% CI: 0.639-0.897, P=0.001). The APP-534G/A site mutation affects the regulation of APP protein expression by miR-101-3p, miR-144-3p, miR-153-3p, and miR-381-3p, and the mutation of the APP-118C/A site affects miR-101-3p, miR-144-3p, miR-153-3p, and miR-383-5p regulation of APP expression. Conclusion: APP 3'UTR polymorphisms can affect the regulation of APP expression by miRNAs and thus affect the occurrence of AD.