Precursors of select GPI-anchored proteins positively regulate GPI biosynthesis under the control of ERAD

We previously reported that glycosylphosphatidylinositol (GPI) biosynthesis is regulated by endoplasmic reticulum associated degradation (ERAD); however, the underlying mechanistic basis remains unclear. Based on a genome-wide CRISPR–Cas9 screen, we show that a widely expressed GPI-anchored protein CD55 precursor and ER-resident ARV1 together upregulate GPI biosynthesis under ERAD-deficient conditions. In cells defective in GPI transamidase, GPI-anchored protein precursors fail to obtain GPI, remaining the uncleaved GPI-attachment signal at the C-termini. We show that ERAD deficiency causes accumulation of the CD55 precursor, which in turn upregulates GPI biosynthesis, where the GPI-attachment signal peptide is the active element. Among the 32 GPI-anchored proteins tested, only the GPI-attachment signal peptides of CD55 and CD48 enhance GPI biosynthesis. ARV1 is essential for the GPI upregulation by CD55 precursor. Our data demonstrate an ARV1-dependent regulatory connection between GPI biosynthesis and precursors of select GPI-anchored proteins that are under the control of ERAD.

Ubiquitin ligase component LRS1 and transcription factor CrHy5 act as a light switch for photoprotection in Chlamydomonas

ABSTRACTSurvival under excess light conditions requires the light-induced accumulation of protein LHCSR3 and other photoprotection factors, to enable efficient energy-dependent quenching in the green microalga Chlamydomonas reinhardtii. Here, we demonstrate that the high light-tolerant phenotype of mutant hit1 is caused by a de-repression of promoters belonging to photoprotection genes, which in turn results from an inactivation of the E3 ubiquitin ligase substrate adaptor LRS1. Transcriptome analyses of hit1 revealed massive alterations of gene expression modulation as a consequence of perturbed LRS1 function, indicating its role as a crown regulator. In conjunction with random forest-based network modeling, these transcriptome analyses predicted that LRS1 controls photoprotection gene expression via an algal HY5 homolog as its prime transcription factor target. CrHY5 binds to T-box elements present in the promoters of these genes and its inactivation in the hit1 mutant via CRISPR-Cas9 genome editing, confirmed the regulatory connection between LRS1 and CrHY5, predicted by the network analysis.

Bringing in the ‘neoliberal model of development’

This article brings in the concept of the ‘neoliberal model of development’ as a corrective to the prevailing emphasis in the literature that usefully describes neoliberalism as a nationally diverging phenomenon but does not adequately examine the mid-range trans-national/global regulatory connection or the logics of national convergence. By extending the concept of regulation and specifying the national trans-national connection, this article revises the original Parisian French Regulation School conception of a ‘model of development’ and makes it applicable to the contemporary neoliberal era. It then applies this revised conception to help explain contemporary patterns of national convergence and divergence. In particular, with reference to Marx’s theory of the ‘relative surplus population’, this article explores capitalism’s uneven development as a form of national variation intensified by the neoliberal model of development. This revisionist analysis of model of development also demonstrates how its praxis dimension is significant for explaining past and present mid-range variations of capitalism, and more importantly for making a mid-range counter-hegemonic future.

Two membrane-bound transcription factors regulate expression of various type-IV-pili surface structures in Sulfolobus acidocaldarius

In Archaea and Bacteria, gene expression is tightly regulated in response to environmental stimuli. In the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius nutrient limitation induces expression of the archaellum, the archaeal motility structure. This expression is orchestrated by a complex hierarchical network of positive and negative regulators—the archaellum regulatory network (arn). The membrane-bound one-component system ArnR and its paralog ArnR1 were recently described as main activators of archaellum expression in S. acidocaldarius. They regulate gene expression of the archaellum operon by targeting the promoter of flaB, encoding the archaellum filament protein. Here we describe a strategy for the isolation and biochemical characterization of these two archaellum regulators. Both regulators are capable of forming oligomers and are phosphorylated by the Ser/Thr kinase ArnC. Apart from binding to pflaB, ArnR but not ArnR1 bound to promoter sequences of aapF and upsX, which encode components of the archaeal adhesive pilus and UV-inducible pili system, demonstrating a regulatory connection between different surface appendages of S. acidocaldarius.

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 Å 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.