TDP-43 regulatesβ-adducin(Add2) transcript stability

Abstract

Keywords: Add2, DSE, mRNA stability, TDP-43, 3 0 end processing, 3 0 UTR Abbreviations: RBP, RNA binding protein, DSE, downstream element, PAS, polyadenylation site, ActD, actinomycin D.TDP-43 is an RNA-binding protein involved in several steps of mRNA metabolism including transcription, splicing and stability. It is also involved in ALS and FTD, neurodegenerative diseases characterized by TDP-43 nuclear depletion. We previously identified TDP-43 as a binder of the downstream element (DSE) of the b-Adducin (Add2) brain-specific polyadenylation site (A4 PAS), suggesting its involvement in pre-mRNA 3 0 end processing. Here, by using chimeric minigenes, we showed that TDP-43 depletion in HeLa and HEK293 cells resulted in down-regulation of both the chimeric and endogenous Add2 transcripts. Despite having confirmed TDP-43-DSE in vitro interaction, we demonstrated that the in vivo effect was not mediated by the TDP-43-DSE interaction. In fact, substitution of the Add2 DSE with viral E-SV40 and L-SV40 DSEs, which are not TDP-43 targets, still resulted in decreased Add2 mRNA levels after TDP-43 downregulation. In addition, we failed to show interaction between TDP-43 and key polyadenylation factors, such as CstF-64 and CPSF160 and excluded TDP-43 involvement in pre-mRNA cleavage and regulation of polyA tail length. These evidences allowed us to exclude the pre-hypothesized role of TDP43 in modulating 3 0 end processing of Add2 pre-mRNA. Finally, we showed that TDP-43 regulates Add2 gene expression levels by increasing Add2 mRNA stability. Considering that Add2 in brain participates in synapse assembly, synaptic plasticity and their stability, and its genetic inactivation in mice leads to LTP, LTD, learning and motor-coordination deficits, we hypothesize that a possible loss of Add2 function by TDP-43 depletion may contribute to ALS and FTD disease states.

Physiological functions and pathobiology of TDP‐43 and FUS/TLS proteins

“…It is therefore not surprising that several other mRNAs whose stability may be specifically affected by TDP‐43 have been recently described, such as Add2 (Costessi et al . ), VEGFA and GRN (Colombrita et al . ), and IL‐6 (Lee et al .…”

The role of ubiquitinated TDP-43 in amyotrophic lateral sclerosis

“…Next, TDP-43 combines with RNA/DNA and regulates RNA metabolism at multiple levels, including transcription, RNA splicing, and mRNA stability. In TDP-43 knockout HeLa cells and HEK293 cell cultures, tdp43 can regulate add2 gene expression by increasing Add2 mRNA stability, which is closely related to synaptic aggregation, synaptic remodeling and stability [7,9] . UTRs at the 3' terminal of TDP-43 protein is a specific mRNAs that is associated with its distribution and aggregation in cells.…”

Deregulation of RNA Metabolism in Microsatellite Expansion Diseases

“…TDP-43 functions in multiple RNA processing steps including pre-mRNA splicing [131–134], RNA stability [135–137] and transport [138]. Similar to TDP-43, FUS interacts with serine-arginine (SR) proteins that serve diverse roles in splicing [139] and regulates transcription by recruiting other RBPs through non-coding RNAs [140].…”