Biology subjects

Tainer, J.

Publications and source records attributed to Tainer, J..

5 recordsLinked to original sources

bioRxiv2024

RNA/DNA Binding Protein TDP43 Regulates DNA Mismatch Repair Genes with Implications for Genome Stability

TDP43 is an RNA/DNA binding protein increasingly recognized for its role in neurodegenerative conditions, including amyotrophic lateral sclerosis and frontotemporal dementia (FTD). As characterized by its aberrant nuclear export and cytoplasmic aggregation, TDP43 proteinopathy is a hallmark feature in over 95% of ALS/FTD cases, leading to the formation of detrimental cytosolic aggregates and a reduction in nuclear functionality within neurons. Building on our prior work linking TDP43 proteinopathy to the accumulation of DNA double-strand breaks (DSBs) in neurons, the present investigation uncovers a novel regulatory relationship between TDP43 and DNA mismatch repair (MMR) gene expressions. Here, we show that TDP43 depletion or overexpression directly affects the expression of key MMR genes. Alterations include MLH1, MSH2, MSH3, MSH6, and PMS2 levels across various primary cell lines, independent of their proliferative status. Our results specifically establish that TDP43 selectively influences the expression of MLH1 and MSH6 by influencing their alternative transcript splicing patterns and stability. We furthermore find aberrant MMR gene expression is linked to TDP43 proteinopathy in two distinct ALS mouse models and post-mortem brain and spinal cord tissues of ALS patients. Notably, MMR depletion resulted in the partial rescue of TDP43 proteinopathy-induced DNA damage and signaling. Moreover, bioinformatics analysis of the TCGA cancer database reveals significant associations between TDP43 expression, MMR gene expression, and mutational burden across multiple cancers. Collectively, our findings implicate TDP43 as a critical regulator of the MMR pathway and unveil its broad impact on the etiology of both neurodegenerative and neoplastic pathologies.

biochemistry↗

bioRxiv2022

A condensate forming tether for lariat debranching enzyme is defective in non-photosensitive trichiothiodystrophy

The pre-mRNA life cycle requires intron processing; yet, how intron processing defects influence splicing and gene expression is unclear. Here, we find TTDN1, which is frequently mutated in non-photosensitive trichothiodystrophy (NP-TTD), functionally links intron lariat processing to the spliceosome. The conserved TTDN1 C-terminal region directly binds lariat debranching enzyme DBR1, while its N-terminal intrinsically disordered region (IDR) binds the intron binding complex (IBC). The IDR forms condensates in vitro and is needed for IBC interaction. TTDN1 loss causes significant intron lariat accumulation, as well as splicing and gene expression defects, mirroring phenotypes observed in NP-TTD patient cells. Ttdn1{Delta}/{Delta} mice recapitulate intron processing defects and neurodevelopmental phenotypes seen in NP-TTD. A DBR1-IDR fusion recruits DBR1 to the IBC and circumvents the requirement for TTDN1, indicating this tethering role as its major molecular function. Collectively, our findings unveil key functional connections between lariat processing, splicing outcomes, and NP-TTD molecular pathology.

biochemistry↗

bioRxiv2022

Identification of unique α4 chain structure and conserved anti-angiogenic activity of α3NC1 type IV collagen in zebrafish

Type IV collagen is an abundant component of basement membranes in all multicellular species and is essential for the extracellular scaffold supporting tissue architecture and function. Lower organisms typically have two type IV collagen genes, encoding 1 and 2 chains, in contrast with the six genes in humans, encoding 1 to 6 chains. The chains assemble into trimeric protomers, the building blocks of the type IV collagen network. The detailed evolutionary conservation of type IV collagen network remains to be studied. We report on the molecular evolution of type IV collagen genes. The zebrafish 4 non-collagenous (NC1) domain, in contrast with its human ortholog, contains an additional cysteine residue and lacks the M93 and K211 residues involved in sulfilimine bond formation between adjacent protomers. This may alter 4 chain interactions with other chains, as supported by temporal and anatomic expression patterns of collagen IV chains during zebrafish development. Despite the divergence between zebrafish and human 3 NC1 domain (endogenous angiogenesis inhibitor, Tumstatin), the zebrafish 3 NC1 domain exhibits conserved anti-angiogenic activity in human endothelial cells. Our work supports type IV collagen is largely conserved between zebrafish and humans, with a possible difference involving the 4 chain.

developmental biology↗

bioRxiv2022

Nardilysin-Regulated Scission Mechanism Activates Polo-like Kinase 3 to Suppress the Development of Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) develops through step-wise genetic and molecular alterations including Kras mutation and inactivation of apoptotic pathways. Here, we find that development of anoikis resistance and metastasis of KrasG12D-driven PDAC in mice is accelerated by deleting Plk3, explaining the often reduced Plk3 expression in human PDAC. Importantly, a 41 kDa Plk3 (p41Plk3) that contained the entire kinase domain at the N-terminus (1-353 aa) is activated by scission of the precursor p72Plk3 at Arg354 by metalloendopeptidase Nardilysin (NRDC), and the resulting p32Plk3 C-terminal Polo-box domain (PBD) was quickly removed by proteasome degradation preventing the p41Plk3 inhibition by PBD. We found that p41Plk3 is the activated form of Plk3 that regulates a feedforward mechanism to promote anoikis and suppress PDAC and metastasis. p41Plk3 phosphorylates c-Fos on Thr164, which in turn, induces expression of Plk3 and pro-apoptotic genes. These findings uncovered an NRDC-regulated post-translational mechanism (PTM) that activates Plk3, establishing a prototypic regulation by scission mechanism.

cancer biology↗

bioRxiv2020

Aberrant RNA methylation triggers recruitment of an alkylation repair complex

A critical question in genome stability is the nature of the chemical damage responsible for repair activation. We previously reported a novel pathway specifically activated during alkylation damage in human cells, where the E3 ubiquitin ligase RNF113A mediates the recruitment of the ASCC repair complex. Yet the mechanistic basis for the alkylation damage selectivity of this pathway remains unclear. Here, we demonstrate that RNA but not DNA alkylation is the initiating signal for this process. Aberrantly methylated RNA is sufficient to recruit ASCC, while an RNA dealkylase suppresses ASCC recruitment during chemical alkylation. This aberrant RNA methylation causes transcriptional repression in a manner dependent on the ASCC complex. We show that an alkylated pre-mRNA, or an RNA containing a single damaged base, is sufficient to activate RNF113A E3 activity in a phosphorylation-dependent manner. Together, our work identifies an unexpected role for RNA damage in eliciting a DNA repair response, and suggests that RNA may serve as the "canary in the coal mine" for sensing alkylation damage.

molecular biology↗