Biology subjects

Moffatt, C.

Publications and source records attributed to Moffatt, C..

3 recordsLinked to original sources

bioRxiv2026

Robust mammalian RNA localization elements are complex and multipartite

The subcellular localization patterns of RNAs are controlled by regulatory elements contained within them. However, for most localized RNAs, the identities of these elements remain unknown. We had previously identified several localization elements that are necessary and sufficient for robust, kinesin-dependent RNA targeting to microtubule plus ends in a variety of cell types. Yet the characteristics of these elements that are critical for function remained unclear. To address this, we systematically created tens of thousands of mutant localization elements and quantified their ability to regulate subcellular RNA localization in neuronal cells. We found that the minimally active size of these localization elements is large, approximately 200 nucleotides. These elements contain multiple important subsequences, with some being completely intolerant of any changes and others being tolerant to a shuffling of nucleotide order but not to changes in nucleotide composition. Using single molecule microscopy, we verified these findings in primary rat neurons. Together, these results demonstrate that highly active mammalian RNA localization elements are large, complex, and multipartite and lay a foundation for further mechanistic studies of their function.

molecular biology↗

bioRxiv2025

TDP-43 directly inhibits RNA accumulation in neurites through modulation of RNA stability

The subcellular localization of hundreds of RNAs to neuronal projections allows neurons to efficiently and rapidly react to spatially restricted external cues. However, for the vast majority of these RNAs, the mechanisms that govern their localization are unknown. Here we demonstrate that the ALS-associated RNA binding protein TDP-43 primarily acts to keep RNAs out of neuronal projections. Using subcellular fractionation and single molecule RNA FISH we find that TDP-43 loss results in the increased neurite accumulation of hundreds of RNAs. These RNAs are highly enriched for known TDP-43 binding sites, suggesting that TDP-43 directly binds them to regulate their localization. We then identified precise regions within RNAs that mediate their TDP-43-dependent localization and interaction with TDP-43 using high-throughput functional assays in cells and high-throughput binding assays in vitro. We found that these regions also mediated TDP-43-dependent RNA instability, identifying the mechanism by which TDP-43 regulates RNA localization. ALS-associated mutations in TDP-43 resulted in similar RNA mislocalization phenotypes as did TDP-43 loss in human iPS-derived motor neurons. These findings establish TDP-43 as a direct negative regulator of RNA abundance in neurites and suggest that mislocalization of specific transcripts may occur in ALS patients.

molecular biology↗

bioRxiv2021

The Mettl3 epitranscriptomic writer amplifies p53 stress responses

The p53 transcription factor, encoded by the most frequently mutated gene in human cancer, plays a critical role in tissue homeostasis in response to stress signals. The mechanisms through which p53 promotes downstream tumor suppressive gene expression programs remain, however, only superficially understood. Here, we used tandem affinity purification and mass spectrometry to reveal new components of the p53 response. This approach uncovered Mettl3, a component of the m6A RNA methyltransferase complex (MTC), as a p53-interacting protein. Analysis of Mettl3- deficient cells revealed that Mettl3 promotes p53 protein stabilization and target gene expression in response to DNA damage. Mettl3 acts in part by competing with the p53 negative regulator, Mdm2, for binding to the p53 transactivation domains to promote methyltransferase-independent stabilization of p53. In addition, Mettl3 relies on its catalytic activity to augment p53 responses, with p53 recruiting Mettl3 to p53 target genes to co-transcriptionally direct m6A modification of p53 pathway transcripts to enhance their expression. Mettl3 also promotes p53 activity downstream of oncogenic signals in vivo, in both allograft and autochthonous lung adenocarcinoma models, suggesting cooperative action of p53 and Mettl3 in tumor suppression. Accordingly, we found in diverse human cancers that mutations in MTC components perturb expression of p53 target genes and that MTC mutations are mutually exclusive with TP53 mutations, suggesting that the MTC enhances the p53 transcriptional program in human cancer. Together, these studies reveal a fundamental role for Mettl3 in amplifying p53 signaling through protein stabilization and epitranscriptome regulation.

cancer biology↗