BAF Complex Maintains Glioma Stem Cells in Pediatric H3K27M Glioma.

Diffuse midline gliomas are uniformly fatal pediatric central nervous system cancers that are refractory to standard-of-care therapeutic modalities. The primary genetic drivers are a set of recurrent amino acid substitutions in genes encoding histone H3 (H3K27M), which are currently undruggable. These H3K27M oncohistones perturb normal chromatin architecture, resulting in an aberrant epigenetic landscape. To interrogate for epigenetic dependencies, we performed a CRISPR screen and show that patient-derived H3K27M-glioma neurospheres are dependent on core components of the mammalian BAF (SWI/SNF) chromatin remodeling complex. The BAF complex maintains glioma stem cells in a cycling, oligodendrocyte precursor cell-like state, in which genetic perturbation of the BAF catalytic subunit SMARCA4 (BRG1), as well as pharmacologic suppression, opposes proliferation, promotes progression of differentiation along the astrocytic lineage, and improves overall survival of patient-derived xenograft models. In summary, we demonstrate that therapeutic inhibition of the BAF complex has translational potential for children with H3K27M gliomas. SIGNIFICANCE: Epigenetic dysregulation is at the core of H3K27M-glioma tumorigenesis. Here, we identify the BRG1-BAF complex as a critical regulator of enhancer and transcription factor landscapes, which maintain H3K27M glioma in their progenitor state, precluding glial differentiation, and establish pharmacologic targeting of the BAF complex as a novel treatment strategy for pediatric H3K27M glioma. See related commentary by Beytagh and Weiss, p. 2730. See related article by Mo et al., p. 2906.

Regulation of GTPase function by autophosphorylation.

A unifying feature of the RAS superfamily is a conserved GTPase cycle by which these proteins transition between active and inactive states. We demonstrate that autophosphorylation of some GTPases is an intrinsic regulatory mechanism that reduces nucleotide hydrolysis and enhances nucleotide exchange, altering the on/off switch that forms the basis for their signaling functions. Using X-ray crystallography, nuclear magnetic resonance spectroscopy, binding assays, and molecular dynamics on autophosphorylated mutants of H-RAS and K-RAS, we show that phosphoryl transfer from GTP requires dynamic movement of the switch II region and that autophosphorylation promotes nucleotide exchange by opening the active site and extracting the stabilizing Mg2+. Finally, we demonstrate that autophosphorylated K-RAS exhibits altered effector interactions, including a reduced affinity for RAF proteins in mammalian cells. Thus, autophosphorylation leads to altered active site dynamics and effector interaction properties, creating a pool of GTPases that are functionally distinct from their non-phosphorylated counterparts.

UPLC-PDA coupled HR-TOF ESI/MS2 -based identification of derivatives produced by whole-cell biotransformation of epothilone A using Nocardia sp. CS692 and a cytochrome P450 overexpressing strain.

Epothilone A, a microtubule-stabilizing agent used as therapeutics for the treatment of cancers, was biotransformed into three metabolites using Nocardia sp. CS692 and recombinant Nocardia overexpressing a cytochrome P450 from Streptomyces venezuelae (PikC). Among three metabolites produced in the biotransformation reaction mixtures, ESI/MS2 analysis predicted two metabolites (M1 and M2) as novel hydroxylated derivatives (M1 is hydroxylated at the C-8 position and M2 is hydroxylated at C-10 position), each with an opened-epoxide ring in their structure. Interestingly, metabolite M3 lacks an epoxide ring and is known as deoxyepothilone A, which is also called epothilone C. Metabolite M1 was produced only in PikC overexpressing strain. The endogenous enzymes of Nocardia sp. catalyzed hydroxylation of epothilone A to produce metabolite M2 and removed epoxide ring to produce metabolite M3. All the metabolites were identified based on UV-vis analysis and rigorous ESI/MS2 fragmentation based on epothilone A standard. The newly produced metabolites are anticipated to display novel cytotoxic effects and could be subjects of further pharmacological studies.

Genome-enabled discovery of anthraquinone biosynthesis in Senna tora.

Senna tora is a widely used medicinal plant. Its health benefits have been attributed to the large quantity of anthraquinones, but how they are made in plants remains a mystery. To identify the genes responsible for plant anthraquinone biosynthesis, we reveal the genome sequence of S. tora at the chromosome level with 526 Mb (96%) assembled into 13 chromosomes. Comparison among related plant species shows that a chalcone synthase-like (CHS-L) gene family has lineage-specifically and rapidly expanded in S. tora. Combining genomics, transcriptomics, metabolomics, and biochemistry, we identify a CHS-L gene contributing to the biosynthesis of anthraquinones. The S. tora reference genome will accelerate the discovery of biologically active anthraquinone biosynthesis pathways in medicinal plants.

Exploring the Nucleophilic N- and S-Glycosylation Capacity of Bacillus licheniformis YjiC Enzyme.

YjiC, a glycosyltransferase from Bacillus licheniformis, is a well-known versatile enzyme for glycosylation of diverse substrates. Although a number of O-glycosylated products have been produced using YjiC, no report has been updated for nucleophilic N-, S-, and C- glycosylation. Here, we report the additional functional capacity of YjiC for nucleophilic N- and S- glycosylation using a broad substrate spectrum including UDP-α-D-glucose, UDP-N-acetyl glucosamine, UDP-N-acetylgalactosamine, UDP-α-D-glucuronic acid, TDP-α-L-rhamnose, TDP-α-D-viosamine, and GDP-α-Lfucose as donor and various amine and thiol groups containing natural products as acceptor substrates. The results revealed YjiC as a promiscuous enzyme for conjugating diverse sugars at amine and thiol functional groups of small molecules applicable for generating glycofunctionalized chemical diversity libraries. The glycosylated products were analyzed using HPLC and LC/MS and compared with previous reports.

Two Trifunctional Leloir Glycosyltransferases as Biocatalysts for Natural Products Glycodiversification.

Two promiscuous Bacillus licheniformis glycosyltransferases, YdhE and YojK, exhibited prominent stereospecific but nonregiospecific glycosylation activity of 20 different classes of 59 structurally different natural and non-natural products. Both enzymes transferred various sugars at three nucleophilic groups (OH, NH2, SH) of diverse compounds to produce O-, N-, and S-glycosides. The enzymes also displayed a catalytic reversibility potential for a one-pot transglycosylation, thus bestowing a cost-effective application in biosynthesis of glycodiversified natural products in drug discovery.

Correction to: Cascade biocatalysis systems for bioactive naringenin glucosides and quercetin rhamnoside production from sucrose.

The name of the author "Yamaguchi Tokutaro" is incorrect for the first and last name has been interchanged. The correct presentation is "Tokutaro Yamaguchi".

Biocatalytic Synthesis of Non-Natural Monoterpene O-Glycosides Exhibiting Superior Antibacterial and Antinematodal Properties.

A promiscuous Bacillus glycosyltransferase (YjiC) was explored for the enzymatic synthesis of monoterpene O-glycosides in vitro and in vivo. YjiC converted seven monoterpenes into 41 different sugar-conjugated novel glycoside derivatives. The whole-cell biotransformation of the same set of monoterpenes exhibited robust enzyme activity to synthesize O-glucosyl derivatives from Escherichia coli. These newly synthesized selected monoterpene-O-glucosyl derivatives exhibited enhanced antibacterial activities against human pathogenic bacteria and antinematodal activities against pine wood nematode Bursaphelenchus xylophilus.

Cascade biocatalysis systems for bioactive naringenin glucosides and quercetin rhamnoside production from sucrose.

Two sustainable and cost-effective cascade enzymatic systems were developed to regenerate uridine diphosphate (UDP)-α-D-glucose and UDP-ß-L-rhamnose from sucrose. The systems were coupled with the UDP generating glycosylation reactions of UDP sugar-dependent glycosyltransferase (UGT) enzymes mediated reactions. As a result, the UDP generated as a by-product of the GT-mediated reactions was recycled. In the first system, YjiC, a UGT from Bacillus licheniformis DSM 13, was used for transferring glucose from UDP-α-D-glucose to naringenin, in which AtSUS1 from Arabidopsis thaliana was used to synthesize UDP-α-D-glucose and fructose as a by-product from sucrose. In the second system, flavonol 7-O-rhamnosyltransferase (AtUGT89C1) from A. thaliana was used to transfer rhamnose from UDP-ß-L-rhamnose to quercetin, in which AtSUS1 along with UDP-ß-L-rhamnose synthase (AtRHM1), also from A. thaliana, were used to produce UDP-ß-L-rhamnose from the same starter sucrose. The established UDP recycling system for the production of naringenin glucosides was engineered and optimized for several reaction parameters that included temperature, metal ions, NDPs, pH, substrate ratio, and enzymes ratio, to develop a highly feasible system for large-scale production of different derivatives of naringenin and other natural products glucosides, using inexpensive starting materials. The developed system showed the conversion of about 37 mM of naringenin into three different glucosides, namely naringenin, 7-O-ß-D-glucoside, naringenin, 4'-O-ß-D-glucoside, and naringenin, 4',7-O-ß-D-diglucoside. The UDP recycling (RCmax) was 20.10 for naringenin glucosides. Similarly, the conversion of quercetin to quercetin 7-O-α-L-rhamnoside reached a RCmax value of 10.0.