Targeting histone methyltransferase EZH2 as cancer treatment
It is widely accepted that epigenetic alterations are associated with different stages of tumour formation and progression in many cancers. Therefore, epigenetic abnormalities in cancers are emerging as important biomarkers and may have therapeutic potential. The polycomb repressive complex 2 (PRC2) is a key epigenetic regulator that catalyses trimethylation of lysine 27 on histone H3 (H3K27me3) via the histone methyltransferase, EZH2, which confers stemness and regulates differentiation during embryonic development. Given these roles of EZH2 and H3K27me3, plastic and dynamic features of cancer cells, especially cancer ste...
Source: Journal of Biochemistry - October 27, 2014 Category: Biochemistry Authors: Kondo, Y. Tags: JB Reviews Source Type: research
A new link between the retrograde actin flow and focal adhesions
The retrograde actin flow, continuous centripetal movement of the cell peripheral actin networks, is widely observed in adherent cells. The retrograde flow is believed to facilitate cell migration when linked to cell adhesion molecules. In this review, we summarize our current knowledge regarding the functional relationship between the retrograde actin flow and focal adhesions (FAs). We also introduce our recent study in which single-molecule speckle (SiMS) microscopy dissected the complex interactions between FAs and the local actin flow. FAs do not simply impede the actin flow, but actively attract and remodel the local ...
Source: Journal of Biochemistry - October 27, 2014 Category: Biochemistry Authors: Yamashiro, S., Watanabe, N. Tags: JB Reviews Source Type: research
The Cys78-Asn88 loop region of the Campylobacter jejuni CstII is essential for {alpha}2,3-sialyltransferase activity: analysis of the His85 mutants
In this study, the role of His85 in the activity of CstII has been investigated by mutating it to Ala, Phe, Trp or Tyr. His85 is found to be essential for α2,3-sialyltransferase activity but not α2,8-sialyltransferase activity. Although no gross changes are observed in secondary and tertiary structures, thermal stability is affected by His85 mutation. MD simulations show changes in the flexibility of the loop regions including those in the binding site. (Source: Journal of Biochemistry)
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Prabhakar, P. K., Rao, K. K., Balaji, P. V. Tags: Regular Papers Source Type: research
Centromeric histone variant CENP-A represses acetylation-dependent chromatin transcription that is relieved by histone chaperone NPM1
Mammalian centromeric histone H3 variant, CENP-A, is involved in maintaining the functional integrity and epigenetic inheritance of the centromere. CENP-A causes transcriptional repression of centromeric chromatin through an unknown mechanism. Here, we report that reconstituted CENP-A nucleosomes are amenable to ATP-dependent SWI/SNF-mediated remodelling but are less permissive to acetylation and acetylation-dependent in vitro chromatin transcription. Remarkably, the transcriptional repression of the CENP-A chromatinized template could be relieved by the ectopic addition of histone chaperone, nucleophosmin. (Source: Journal of Biochemistry)
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Shandilya, J., Senapati, P., Hans, F., Menoni, H., Bouvet, P., Dimitrov, S., Angelov, D., Kundu, T. K. Tags: Regular Papers Source Type: research
Mutational analysis of charged residues in the cytoplasmic loops of MotA and MotP in the Bacillus subtilis flagellar motor
Bacterial flagellar motors are energized by a proton (H+) or sodium ion (Na+) motive force. The motor torque is generated by the interactions between a rotor and about a dozen stators at the interface. MotAB-type stators use H+, whereas MotPS- and PomAB-type stators use Na+ as the coupling ion. In Escherichia coli, the cytoplasmic loop of MotA contains charged residues that interact with conserved charged residues in a rotor protein FliG. Bacillus subtilis has two distinct stator elements MotAB and MotPS. Both stator elements contribute to torque generation by the flagellar motor. To clarify the roles of conserved charged ...
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Takahashi, Y., Ito, M. Tags: Regular Papers Source Type: research
Identification of the roles of individual amino acid residues of the helix E of the major antenna of photosystem II (LHCII) by alanine scanning mutagenesis
The functions of the helix E (W97-F105), an amphiphilic lumenal 310 helix of the major antenna of photosystem II (LHCII), are still unidentified. To elucidate the roles of individual amino acid residue of the helix E, alanine scanning mutagenesis has been performed to mutate every residue of this domain to alanine. The influence of every alanine substitution on the structure and function of LHCII has been investigated biochemically and spectroscopically. The results show that all mutations have little impact on the pigment binding and configuration. However, many mutants presented decreased thermo- or photo-stability compa...
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Liu, C., Rao, Y., Zhang, L., Yang, C. Tags: Regular Papers Source Type: research
Molecular mechanism of intramembrane proteolysis by {gamma}-secretase
Presenilin is a membrane-embedded intramembrane-cleaving protease with a conserved catalytic GxGD motif. It is the catalytic subunit of -secretase, which plays critical roles in developmental biology and the molecular etiology of Alzheimer disease, together with three membrane protein cofactors, nicastrin, Aph-1 and Pen-2. Biochemical and enzymatic analyses have revealed that -secretase executes two types of proteolytic activities on a single substrate; an endopeptidase-like cleavage followed by carboxypeptidase-like processive cleavage. Utilizing small molecule inhibitors/modulators together with the substituted cysteine ...
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Tomita, T. Tags: JB Reviews Source Type: research
Molecular properties of the high-affinity choline transporter CHT1
This article summarizes molecular properties of the high-affinity choline transporter (CHT1) with reference to the historical background focusing studies performed in laboratories of the author. CHT1 is present on the presynaptic terminal of cholinergic neurons, and takes up choline which is the precursor of acetylcholine. The Na+-dependent uptake of choline by CHT1 is the rate-limiting step for synthesis of acetylcholine. CHT1 is the integral membrane protein with 13 transmembrane segments, belongs to the Na+/glucose co-transporter family (SLC5), and has 20–25% homology with members of this family. A single nucleoti...
Source: Journal of Biochemistry - September 29, 2014 Category: Biochemistry Authors: Haga, T. Tags: JB Reviews Source Type: research
Reaction mechanism of Zn2+-dependent D-serine dehydratase: role of a conserved tyrosine residue interacting with pyridine ring nitrogen of pyridoxal 5'-phosphate
d-Serine dehydratase from Saccharomyces cerevisiae (Dsd1p) is a pyridoxal 5'-phosphate (PLP)- and Zn2+-dependent enzyme that catalyzes the dehydration of d-serine to yield pyruvate and ammonia. Dsd1p uses the Tyr residue (Y203) to interact with the pyridine nitrogen of PLP, which is a unique feature of PLP enzymes. To investigate the role of Y203 in catalysis, a series of Y203 mutants was constructed and studied. Mutant enzymes possessing a non-polar or a basic residue instead of Y203 (Y203F, A, S and R) exhibited substantial levels of catalytic activity, and among these, the Y203F mutant had the least impact on catalytic ...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Ito, T., Matsuoka, M., Koga, K., Hemmi, H., Yoshimura, T. Tags: Regular Papers Source Type: research
Mechanistic studies on formation of the dinitrosyl iron complex of the [2Fe-2S] cluster of SoxR protein
The transcriptional activation of SoxR in Escherichia coli occurs through direct modification of the [2Fe-2S] by nitric oxide (NO) to form a dinitrosyl iron complex (DNIC). Here, we investigated the reactions of NO with [2Fe-2S] clusters of SoxR; the results were compared with those obtained for spinach ferredoxin (Fd). UV-visible absorption and ESR spectra of SoxR upon treatment with an NO donor showed the formation of DNIC of SoxR efficiently, whereas those of Fd exhibited small changes. Upon pulse radiolysis of a deaerated solution of SoxR in the presence of sodium nitrite, a biphasic change in absorption, consisting of...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Fujikawa, M., Kobayashi, K., Kozawa, T. Tags: Regular Papers Source Type: research
The staphylococcal elastin-binding protein regulates zinc-dependent growth/biofilm formation
Staphylococcus aureus is one of the most important human pathogens because it is a common cause of nosocomial infections. The elastin-binding protein of Staphylococcus aureus (EbpS) is an adhesin that is responsible for attachment to host cells via its binding to elastin. Despite its relatively weak contribution to adhesion, the ebpS gene is highly conserved among S. aureus isolates, suggesting that EbpS may have other crucial functions. Here, we found that EbpS binds Zn2+ with its N-terminal region, which leads to local conformational changes that result in the assembly of the EbpS protein. The growth rate of the EbpS-def...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Nakakido, M., Aikawa, C., Nakagawa, I., Tsumoto, K. Tags: Regular Papers Source Type: research
TandeMBP: generation of a unique protein substrate for protein kinase assays
In this study, to obtain more efficient substrates for protein kinase assays than commercially available MBP from bovine brain, we produced various recombinant MBPs using Escherichia coli expression systems. Three splice isoforms of mouse MBP were expressed in E. coli and successfully purified using a new protocol consisting of HCl extraction, urea treatment and affinity purification with HiTrap Chelating HP column. The recombinant MBP isoforms thus obtained served as more efficient substrates for protein kinases than MBP isolated from bovine brain. To generate an even better substrate for protein kinase assays, we produce...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Kameshita, I., Yamashita, S., Katayama, S., Senga, Y., Sueyoshi, N. Tags: Regular Papers Source Type: research
Activated K-RAS and its effect on morphological appearance
RAS genes are frequently mutated in various human tumours. These mutations cause GTPase RAS to remain locked in constitutively active signals through the downstream cascades leading to proliferation. A series of earlier studies reported on the morphological appearance of cells upon RAS activation. Classically, morphologic changes of fibroblasts have been used to confirm the oncogenic activity of RAS. Recent works found that the active RAS induces benign and malignant morphological changes in organoids, which are an in vitro model system for epithelial tissue. The studies of animal models support the basic oncogenic feature...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Kiyokawa, E., Minato, H. Tags: JB Reviews Source Type: research
Dissecting tumour heterogeneity in flies: genetic basis of interclonal oncogenic cooperation
Cancers develop through sequential acquisition of oncogenic mutations, indicating a crucial role of genetic alterations in tumour progression. However, accumulating evidence suggests that cancers also progress towards malignancy through cell–cell interactions within heterogeneous tumour tissue. Recent studies have indicated that tumour heterogeneity not only contributes to drug resistance and tumour recurrence but also plays an active role in promoting tumour progression. Especially, genetic studies in Drosophila have discovered novel types of tumour progression through cell–cell interactions and have dissected...
Source: Journal of Biochemistry - August 27, 2014 Category: Biochemistry Authors: Ohsawa, S., Takemoto, D., Igaki, T. Tags: JB Reviews Source Type: research
aPKC{lambda} maintains the integrity of the glomerular slit diaphragm through trafficking of nephrin to the cell surface
In conclusion, the regulation of SD turnover by aPKC is crucial for the maintenance of SD integrity and defects in aPKC signalling can lead to proteinuria. These findings not only reveal the pivotal importance of the dynamic turnover of cell-surface SD components but also suggest a novel pathophysiological basis in glomerular disease. (Source: Journal of Biochemistry)
Source: Journal of Biochemistry - July 28, 2014 Category: Biochemistry Authors: Satoh, D., Hirose, T., Harita, Y., Daimon, C., Harada, T., Kurihara, H., Yamashita, A., Ohno, S. Tags: Regular Papers Source Type: research
