Hansol Lee

YB1/p32, a nuclear Y-box binding protein 1, is a novel regulator of myoblast differentiation that interacts with Msx1 homeoprotein

Precisely controlled cellular differentiation is essential for the proper development of vertebrate embryo and deregulated differentiation is a major cause of many human congenital diseases as well as cancer. Msx1 is a member of the homeoprotein family implicated in these processes, which inhibits the differentiation of skeletal muscle and other cell types, presumably by regulating transcription of target genes through interaction with other cellular factors. We presently show that YB1/p32, a nuclear Y-box binding protein 1, interacts with Msx1 homeoprotein and functions as a regulator of C2C12 myoblast differentiation. We demonstrate that YB1/p32 functionally interacts with Msx1 through its N-terminal region and colocalizes with Msx1 at the nuclear periphery. Moreover, we find that YB1/p32 is competent for inhibition of C2C12 myoblast differentiation, which is correlated with its activity as a negative regulator of MyoD gene expression and binding to the MyoD core enhancer region (CER). Furthermore, YB1/p32 cooperates with Msx1 in transcriptional repression and knocking down the expression of endogenous YB1 attenuates the effects of Msx1. Taken together, our study has uncovered a new function of YB1/p32, a regulator of skeletal muscle differentiation.

14-3-3ε protein increases matrix metalloproteinase-2 gene expression via p38 MAPK signaling in NIH3T3 fibroblast cells

One of the 14-3-3 protein isoforms, 14-3-3ɛ, was previously shown to be increased during skin aging. We suggest here a possible role for the 14-3-3ɛ protein in skin aging by providing evidence that 14-3-3ɛ increases the expression of the matrix-metalloproteinase (MMP)-2 gene in NIH3T3 fibroblast cells. Expression of the 14-3-3ɛ gene in NIH3T3 cells primarily up-regulated the expression of the MMP-2 gene at the transcriptional level by inducing specific DNA binding proteins bound to an upstream region of the MMP-2 promoter from -1,629 to -1,612. Inhibition of endogenous 14-3-3ɛ gene expression by RNA interference also decreased endogenous MMP-2 gene expression. Furthermore, up-regulation of the MMP-2 gene by 14-3-3ɛ was suppressed by expression of a dominant-negative mutant of p38 MAP kinase. These findings strongly suggest that increased expression of 14-3-3ɛ contributes to remodeling of extracellular matrix in skin through increasing MMP-2 gene expression via p38 MAP kinase signaling.

Setdb1 Is Required for Myogenic Differentiation of C2C12 Myoblast Cells via Maintenance of MyoD Expression

Setdb1, an H3-K9 specific histone methyltransferase, is associated with transcriptional silencing of euchromatic genes through chromatin modification. Functions of Setdb1 during development have been extensively studied in embryonic and mesenchymal stem cells as well as neurogenic progenitor cells. But the role of Sedtdb1 in myogenic differentiation remains unknown. In this study, we report that Setdb1 is required for myogenic potential of C2C12 myoblast cells through maintaining the expressions of MyoD and muscle-specific genes. We find that reduced Setdb1 expression in C2C12 myoblast cells severely delayed differentiation of C2C12 myoblast cells, whereas exogenous Setdb1 expression had little effect on. Gene expression profiling analysis using oligonucleotide micro-array and RNA-Seq technologies demonstrated that depletion of Setdb1 results in downregulation of MyoD as well as the components of muscle fiber in proliferating C2C12 cells. In addition, exogenous expression of MyoD reversed transcriptional repression of MyoD promoter-driven lucif-erase reporter by Setdb1 shRNA and rescued myogenic differentiation of C2C12 myoblast cells depleted of endogenous Setdb1. Taken together, these results provide new insights into how levels of key myogenic regulators are maintained prior to induction of differentiation.

Impaired avoidance learning and increased hsp70 mRNA expression in pentylenetetrazol‐treated zebrafish

Abstract The effects of pentylenetetrazol (PTZ), a GABA receptor antagonist, were studied on passive avoidance learning and expression of heat shock protein 70 (hsp70), neuroglobin, and fatty acid binding protein‐7 (fabp‐7) genes. Zebrafish were trained to stay in a dark compartment to avoid a weight dropping in an acryl shuttle box with a central sliding door. In two training sessions of 2 h interval, each consisting of 3 trials, the crossing time was significantly increased from 43.2±14.4s to 149.3±38.5s in the first training session and remained 116.1 ±36.0 s in the first trial of the second training session in the control. In zebrafish treated with PTZ before the first training session, the crossing time was significantly increased neither in the first nor in the second training session. However, the increased crossing time was maintained in the second training session when 10 mM PTZ was treated three times for 10 min at 30 min intervals between the first and second training session. Quantitative real‐time PCR showed that expression level of hsp70 mRNA increased two to eight fold over that of control in the brain at 0–24 h after termination of PTZ treatment. No change in expression of neuroglobin and fabp‐7 mRNA was shown in PTZ‐treated zebrafish. Our studies suggest that PTZ impairs learning ability in avoidance response and also modifies expression of genes related to the neuroprotection.

Mesonia aquimarina sp. nov., a marine bacterium isolated from coastal seawater

A Gram-staining-negative, aerobic, yellow, non-flagellated, non-gliding, rod-shaped bacterium, designated strain IMCC1021(T), was isolated off the coast of the East Sea. Optimal growth of strain IMCC1021(T) was observed at 25 °C, pH 7.0-7.5 and in the presence of 3.0-3.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain belonged to the genus Mesonia, showing a close relationship with Mesonia mobilis KMM 6059(T) (97.4 % similarity) followed by Mesonia phycicola MDSW-25(T) (96.1 %). DNA-DNA relatedness between strain IMCC1021(T) and M. mobilis KMM 6059(T) was 17.5 % (reciprocal 7.4 %), which indicated that the new isolate represents a novel genomic species of the genus Mesonia. The major fatty acids were iso-C15 : 0 and iso-C17 : 0 3-OH, and the G+C content of the genomic DNA was 41.4 mol%. Strain IMCC1021(T) contained menaquinone-6 (MK-6) as the respiratory quinone, and polar lipids comprising phosphatidylethanolamine, two unknown aminolipids and three unknown polar lipids. On the basis of the phylogenetic distinctions and differential phenotypic characteristics, it is suggested that strain IMCC1021(T) ( = KCTC 32320(T) = NBRC 109485(T)) should be assigned to the genus Mesonia as the type strain of a novel species, for which the name Mesonia aquimarina sp. nov. is proposed.

PIAS1 negatively regulates ubiquitination of Msx1 homeoprotein independent of its SUMO ligase activity.

Posttranslational modifications play key roles in many cellular processes including proliferation and differentiation by modulating the activities of target proteins. PIAS1, a member of PIAS family of protein, mediates the modification of protein by SUMO and thereby regulates the function of its interacting protein partners. Here we report that PIAS1 negatively regulates ubiquitination of Msx1 homeoprotein, a regulator of myogenic differentiation, in a SUMOindependent manner. We demonstrate that ubiquitination and SUMOylation of Msx1 are not mutually exclusive but require the same C-terminal PIAS1 interaction domain. In addition, deletion of C-terminal domain increases the steady-state protein level of Msx1, while mutations of SUMO acceptor sites have no significant effect on the stability of Msx1 proteins. Moreover, we find that forced expression of PIAS1 inhibits ubiquitination and thereby increases the stability of Msx1 protein regardless of its activity as a SUMO ligase. Furthermore, repressor activity of Msx1 in transcription is strengthened in the presence of PIAS1. Taken together, our studies uncover a new function of PIAS1, which is to control the stability of its interacting protein partner in a SUMO independent manner.

The histone demethylase KDM4B interacts with MyoD to regulate myogenic differentiation in C2C12 myoblast cells

Enzymes that mediate posttranslational modifications of histone and nonhistone proteins have been implicated in regulation of skeletal muscle differentiation. However, functions of histone demethylases that could counter the actions of H3-K9 specific histone methyltransferases remain still obscure. Here we present evidences that KDM4B histone demethylase regulates expression of myogenic regulators such as MyoD and thereby controls myogenic differentiation of C2C12 myoblast cells. We demonstrate that expression of KDM4B gradually increases during myogenic differentiation and depletion of KDM4B using shRNA results in inhibition of differentiation in C2C12 myoblast cells, which is correlated with decreased expression of MyoD and myogenin. In addition, we find that KDM4B shRNA represses expression of MyoD promoter-driven luciferase reporter and exogenous expression of MyoD rescues myogenic potential in KDM4B-depleted myoblast cells. We further show that KDM4B interacts with MyoD, binds to MyoD and myogenin promoters in vivo, and finally, is involved in demethylation of tri-methylated H3-K9 on promoters of MyoD and myogenin. Taken together, our data suggest that KDM4B plays key roles in myogenic differentiation of C2C12 cells, presumably by its function as a H3-K9 specific histone demethylase.

Distribution Pattern of White Snakeroot as an Invasive Alien Plant and Restoration Strategy to Inhibit Its Expansion in Seoripool Park, Seoul

White snakeroot (Ageratina altissima (L.) R. King & H. Robinson) as an invasive alien plant appeared more abundantly at lower elevations where frequent artificial interferences prevailed than at higher elevations where such impacts were less. They appeared abundantly in introduced forests such as black locust plantation but they did not appear or were rare in natural forests such as oak forest. But an exceptional phenomenon where white snakeroot did not appear was found in a Korean pine stand with dense cover afforested recently. Appearance status of white snakeroot in each section of trampling path depended on breadth of the path and relative light intensity. Growth of white snakeroot measured as the number of ramet per genet, height, and biomass was better near the trampling path and was reduced toward the forest interior. The growth was proportionate to the relative light intensity measured according to distance from the trampling path. Such results support the fact generally known in relation to invasion and expansion of the invasive alien plants. From this viewpoint, we suggest a management plan that applies ecological restoration principles to address ecosystems infected with white snakeroot by restoring the integral feature of the degraded nature and more thoroughly conserving the remaining nature.