Baumgartner, M. | Search bioRxiv

bioRxiv2018

Structural basis of human 5,10-methylenetetrahydrofolate reductase (MTHFR) regulation by phosphorylation and S-adenosylmethionine inhibition

The folate and methionine cycles are crucial to the biosynthesis of lipids, nucleotides and proteins, and production of the global methyl donor S-adenosylmethionine (SAM). 5,10-methylenetetrahydrofolate reductase (MTHFR) represents a key regulatory connection between these cycles, generating 5-methyltetrahydrofolate for initiation of the methionine cycle, and undergoing allosteric inhibition by its end product SAM. Our 2.5 [A] resolution crystal structure of human MTHFR reveals a unique architecture, appending the well-conserved catalytic TIM-barrel to a eukaryote-only SAM-binding domain. The latter domain of novel fold provides the predominant interface for MTHFR homo-dimerization, positioning the N-terminal serine-rich phosphorylation region into proximity with the C-terminal SAM-binding domain. This explains how MTHFR phosphorylation, identified on 11 N-terminal residues (16-total), increases sensitivity to SAM binding and inhibition. Finally, we demonstrate the 25-amino-acid inter-domain linker enables conformational plasticity and propose it to be a key mediator of SAM regulation.

biochemistry↗

bioRxiv2017

Minor spliceosome inactivation in the developing mouse cortex causes self-amplifying radial glial cell death and microcephaly.

Inactivation of the minor spliceosome has been linked to microcephalic osteodysplastic primordial dwarfism type 1 (MOPD1). To interrogate how minor intron splicing regulates cortical development, we employed Emx1-Cre to ablate Rnu11, which encodes the minor spliceosome-specific U11 small nuclear RNA (snRNA), in the developing cortex (pallium). Rnu11 cKO mice were born with microcephaly, caused by death of self-amplifying radial glial cells (RGCs). However, both intermediate progenitor cells (IPCs) and neurons were produced in the U11-null pallium. RNAseq of the pallium revealed elevated minor intron retention in the mutant, particularly in genes regulating cell cycle. Moreover, the only downregulated minor intron-containing gene (MIG) was Spc24, which regulates kinetochore assembly. These findings were consistent with the observation of fewer RGCs entering cytokinesis prior to RGC loss, underscoring the requirement of minor splicing for cell cycle progression in RGCs. Overall, we provide a potential explanation of how disruption of minor splicing might cause microcephaly in MOPD1.\n\nSummary StatementHere we report the first mammalian model to investigate the role of the minor spliceosome in cortical development and microcephaly.\n\nList of abbreviations usedMOPD1=microcephalic osteodysplastic primordial dwarfism type 1; snRNA=small nuclear RNA; cKO=conditional knockout; NPC=neural progenitor cell; RGC=radial glial cell; IPC=intermediate progenitor cell; MIG=minor intron-containing gene

developmental biology↗