LPS injection reprograms the expression and the 3′ UTR of a CAP gene by alternative polyadenylation and the formation of a GAIT element in Ciona intestinalis

Abstract

a b s t r a c tThe diversification of cellular functions is one of the major characteristics of multicellular organisms which allow cells to modulate their gene expression, leading to the formation of transcripts and proteins with different functions and concentrations in response to different stimuli. CAP genes represent a widespread family of proteins belonging to the cysteine-rich secretory protein, antigen 5 and pathogenesis-related 1 superfamily which, it has been proposed, play key roles in the infection process and the modulation of immune responses in host animals. The ascidian Ciona intestinalis represents a group of proto-chordates with an exclusively innate immune system that has been widely studied in the field of comparative and developmental immunology. Using this biological system, we describe the identification of a novel APA mechanism by which an intronic polyadenylation signal is activated by LPS injection, leading to the formation of a shorter CAP mRNA capable of expressing the first CAP exon plus 19 amino acid residues whose sequence is contained within the first intron of the annotated gene. Furthermore, such an APA event causes the expression of a translational controlling cis-acting GAIT element which is not present in the previously isolated CAP isoform and identified in the 3 -UTR of other immunerelated genes, suggesting an intriguing scenario in which both transcriptional and post-transcriptional control mechanisms are involved in the activation of the CAP gene during inflammatory response in C. intestinalis.

Transcriptional and in silico analyses of MIF cytokine and TLR signalling interplay in the LPS inflammatory response of Ciona robusta

“…In humans, GAIT elements are implicated in several immune-related mRNAs, showing an important role in gene-specific translation control in innate immunity 54 . In C. robusta, GAIT elements have already been identified in Cap 55 and Tnf-α 56 and in Mif mRNAs 45 . Notably, in C. robusta, Mifs also seem to regulate Mmp9, which has several important immune functions, such as extracellular matrix degradation and Tnf-α and Tgf-β activation 57 .…”

The GAIT translational control system

“…The urochordate sea squirt Ciona intestinalis exhibits a structural equivalent of a GAIT element in the 3 0 -UTR of a CAP gene member of the cysteine-rich secretory protein, antigen 5 and pathogenesis-related 1 superfamily thought to be involved in modulation of host immune responses. 130 Interestingly, formation of the GAIT is regulated, and only forms when the organism is challenged with LPS, consistent with a role in innate immunity. Genome sequencing of C. intestinalis revealed that EPRS mRNA contains two WHEP domains comparable to the RNA-binding, upstream pair of WHEP domains in the human ortholog, suggesting a potential GAIT element-binding activity of EPRS and GAIT-mediated innate immune function.…”

“…There is no experimental evidence for the presence of GAIT function in more complex, i.e., bilaterial, metazoans other than mice and humans. The urochordate sea squirt Ciona intestinalis exhibits a structural equivalent of a GAIT element in the 3′‐UTR of a CAP gene member of the cysteine‐rich secretory protein, antigen 5 and pathogenesis‐related 1 superfamily thought to be involved in modulation of host immune responses . Interestingly, formation of the GAIT is regulated, and only forms when the organism is challenged with LPS, consistent with a role in innate immunity.…”

Literature review of baseline information on non‐coding RNA (ncRNA) to support the risk assessment of ncRNA‐based genetically modified plants for food and feed

“…LPS) has been described (Vizzini et al, 2016). In the ascidian Ciona intestinalis a novel alternative polyadenylation signal activated by the prototypical TLR4 agonist (i.e.…”