Byung Ouk Park

Bio: Byung Ouk Park is an academic researcher from Gyeongsang National University. The author has contributed to research in topics: Fusion protein & Binding site. The author has an hindex of 15, co-authored 19 publications receiving 1714 citations. Previous affiliations of Byung Ouk Park include Stanford University.

PI(3,4,5)P3 and PI(4,5)P2 lipids target proteins with polybasic clusters to the plasma membrane.

Abstract: Many signaling, cytoskeletal, and transport proteins have to be localized to the plasma membrane (PM) in order to carry out their function. We surveyed PM-targeting mechanisms by imaging the subcellular localization of 125 fluorescent protein–conjugated Ras, Rab, Arf, and Rho proteins. Out of 48 proteins that were PM-localized, 37 contained clusters of positively charged amino acids. To test whether these polybasic clusters bind negatively charged phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] lipids, we developed a chemical phosphatase activation method to deplete PM PI(4,5)P2. Unexpectedly, proteins with polybasic clusters dissociated from the PM only when both PI(4,5)P2 and phosphatidylinositol 3,4,5-trisphosphate [PI(3,4,5)P3] were depleted, arguing that both lipid second messengers jointly regulate PM targeting.

BWMK1, a Rice Mitogen-Activated Protein Kinase, Locates in the Nucleus and Mediates Pathogenesis-Related Gene Expression by Activation of a Transcription Factor

Abstract: Mitogen-activated protein kinase (MAPK) cascades are known to transduce plant defense signals, but the downstream components of the MAPK have as yet not been elucidated. Here, we report an MAPK from rice (Oryza sativa), BWMK1, and a transcription factor, OsEREBP1, phosphorylated by the kinase. The MAPK carries a TDY phosphorylation motif instead of the more common TEY motif in its kinase domain and has an unusually extended C-terminal domain that is essential to its kinase activity and translocation to the nucleus. The MAPK phosphorylates OsEREBP1 that binds to the GCC box element (AGCCGCC) of the several basic pathogenesis-related gene promoters, which in turn enhances DNA-binding activity of the factor to the cis element in vitro. Transient co-expression of the BWMK1 and OsEREBP1 in Arabidopsis protoplasts elevates the expression of the β-glucuronidase reporter gene driven by the GCC box element. Furthermore, transgenic tobacco (Nicotiana tabacum) plants overexpressing BWMK1 expressed many pathogenesis-related genes at higher levels than wild-type plants with an enhanced resistance to pathogens. These findings suggest that MAPKs contribute to plant defense signal transduction by phosphorylating one or more transcription factors.

Plasma cell survival in the absence of B cell memory

Abstract: Pre-existing serum antibodies play an important role in vaccine-mediated protection against infection but the underlying mechanisms of immune memory are unclear. Clinical studies indicate that antigen-specific antibody responses can be maintained for many years, leading to theories that reactivation/differentiation of memory B cells into plasma cells is required to sustain long-term antibody production. Here, we present a decade-long study in which we demonstrate site-specific survival of bone marrow-derived plasma cells and durable antibody responses to multiple virus and vaccine antigens in rhesus macaques for years after sustained memory B cell depletion. Moreover, BrdU+ cells with plasma cell morphology can be detected for 10 years after vaccination/BrdU administration, indicating that plasma cells may persist for a prolonged period of time in the absence of cell division. On the basis of these results, long-lived plasma cells represent a key cell population responsible for long-term antibody production and serological memory.

Genome-Wide Analysis of the ERF Gene Family in Arabidopsis and Rice

Abstract: Genes in the ERF family encode transcriptional regulators with a variety of functions involved in the developmental and physiological processes in plants. In this study, a comprehensive computational analysis identified 122 and 139 ERF family genes in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa L. subsp. japonica), respectively. A complete overview of this gene family in Arabidopsis is presented, including the gene structures, phylogeny, chromosome locations, and conserved motifs. In addition, a comparative analysis between these genes in Arabidopsis and rice was performed. As a result of these analyses, the ERF families in Arabidopsis and rice were divided into 12 and 15 groups, respectively, and several of these groups were further divided into subgroups. Based on the observation that 11 of these groups were present in both Arabidopsis and rice, it was concluded that the major functional diversification within the ERF family predated the monocot/dicot divergence. In contrast, some groups/subgroups are species specific. We discuss the relationship between the structure and function of the ERF family proteins based on these results and published information. It was further concluded that the expansion of the ERF family in plants might have been due to chromosomal/segmental duplication and tandem duplication, as well as more ancient transposition and homing. These results will be useful for future functional analyses of the ERF family genes.

Sub1A is an ethylene-response-factor-like gene that confers submergence tolerance to rice

Abstract: Most Oryza sativa cultivars die within a week of complete submergence--a major constraint to rice production in south and southeast Asia that causes annual losses of over US 1 billion dollars and affects disproportionately the poorest farmers in the world. A few cultivars, such as the O. sativa ssp. indica cultivar FR13A, are highly tolerant and survive up to two weeks of complete submergence owing to a major quantitative trait locus designated Submergence 1 (Sub1) near the centromere of chromosome 9 (refs 3, 4, 5-6). Here we describe the identification of a cluster of three genes at the Sub1 locus, encoding putative ethylene response factors. Two of these genes, Sub1B and Sub1C, are invariably present in the Sub1 region of all rice accessions analysed. In contrast, the presence of Sub1A is variable. A survey identified two alleles within those indica varieties that possess this gene: a tolerance-specific allele named Sub1A-1 and an intolerance-specific allele named Sub1A-2. Overexpression of Sub1A-1 in a submergence-intolerant O. sativa ssp. japonica conferred enhanced tolerance to the plants, downregulation of Sub1C and upregulation of Alcohol dehydrogenase 1 (Adh1), indicating that Sub1A-1 is a primary determinant of submergence tolerance. The FR13A Sub1 locus was introgressed into a widely grown Asian rice cultivar using marker-assisted selection. The new variety maintains the high yield and other agronomic properties of the recurrent parent and is tolerant to submergence. Cultivation of this variety is expected to provide protection against damaging floods and increase crop security for farmers.

Phosphoinositides: Tiny Lipids With Giant Impact on Cell Regulation

Abstract: Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.

Membrane phosphatidylserine regulates surface charge and protein localization

Abstract: Electrostatic interactions with negatively charged membranes contribute to the subcellular targeting of proteins with polybasic clusters or cationic domains. Although the anionic phospholipid phosphatidylserine is comparatively abundant, its contribution to the surface charge of individual cellular membranes is unknown, partly because of the lack of reagents to analyze its distribution in intact cells. We developed a biosensor to study the subcellular distribution of phosphatidylserine and found that it binds the cytosolic leaflets of the plasma membrane, as well as endosomes and lysosomes. The negative charge associated with the presence of phosphatidylserine directed proteins with moderately positive charge to the endocytic pathway. More strongly cationic proteins, normally associated with the plasma membrane, relocalized to endocytic compartments when the plasma membrane surface charge decreased on calcium influx.