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ARMC5 controls the degradation of most Pol II subunits, and ARMC5 mutation increases neural tube defect risks in mice and humans

ABSTRACT: ARMC5 is an armadillo domain (ARM)-containing protein. We found that Armc5 KO mice had an increased incidence of neural tube defects (NTDs). ARMC5 is the substrate recognition component of a ubiquitin ligase that targets POLR2A, the largest subunit of RNA polymerase II (Pol II). Surprisingly, the absence of ARMC5 caused the accumulation of not only POLR2A, but most of the other 11 Pol II subunits associated with POLR2A, indicating that the degradation of the whole Pol II complex is compromised. This did not lead to generalized Pol II stalling or a generalized decrease in mRNA transcription. In neural progenitor cells, ARMC5 KO only dysregulated 106 genes, some of which are known to be involved in neural tube development. FOLH1, critical for folate metabolism and vital in neural tube development, was downregulated in the KO intestine, suggesting that it is a downstream effector gene for NTD. To assess whether ARMC5 gene mutation was associated with human NTD, we conducted whole-exome sequencing of 511 patients with myelomeningocele, a severe form of NTD. Nine deleterious single nucleotide variants were discovered in the ARMC5 coding sequence. Four of them were validated in that they weakened the interaction between ARMC5 and POLR2A; consequently, POLR2A ubiquitination was decreased. This proves that our findings in mice are relevant to human NTD; it also supports the role of Pol II in mediating NTD pathogenesis. Our findings indicate that mutations in ARMC5 increase the risk of NTD and support the role of Pol II in NTD pathogenesis. Further investigation is needed to determine the cause-and-effect relationship between an enlarged Pol II pool and NTD and to validate the potential role of downregulated FOLH1 expression in NTD pathogenesis.

INSTRUMENT(S): Orbitrap Fusion

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Hek-293 Cell

SUBMITTER: Christian Poitras

LAB HEAD: Benoit Coulombe

PROVIDER: PXD047533 | Pride | 2023-12-06

REPOSITORIES: Pride

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ARMC5 controls the degradation of most Pol II subunits, and ARMC5 mutation increases neural tube defect risks in mice and humans

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