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M Phase-Specific Phosphorylation of DNA Topoisomerase IIα in HeLa Cells
Bae, Young-Seuk,Lee, Sook-Ja,Kwak, Sang-Soo Korean Society for Biochemistry and Molecular Biol 1996 Journal of biochemistry and molecular biology Vol.29 No.1
Using topoisomerase II (topo II) isozyme-specific antibodies, we investigated the phosphorylation of topo $II{\alpha}$ in mitotic HeLa cells. Topo $II{\alpha}$ was specifically modified in the mitotic cells, resulting in slow migration on SDS-polyacrylamide gel electrophoresis. To characterize the nature of this modification, we treated the nuclear extracts prepared from the mitotic cells with alkaline phosphatase. After the treatment with alkaline phosphatase, the slowly migrated band disappeared and instead a normal (170 kDa) topo $II{\alpha}$ band appeared. These results indicate that human topo $II{\alpha}$ is modified at a specific site(s) in M phase by phosphorylation, supporting the possibility that M phase-specific phosphorylation of topo II is critical for mitotic chromosome condensation and segregation.
The βSubunit of CKⅡ Interacts with the Lysosomal Protease Cathepsin L
Bae, Young-Seuk,Yu, Hyun-Jae,Ahn, Bong-Hyun The Korea Science and Technology Center 1998 BMB Reports Vol.31 No.6
Protein kinase CKII(CKII) is a protein Ser/Thr kinase that is ubiquitously distributed in eukaryotic cells. Although it has been suggested that CKII plays an critical role in cell growth and proliferation, its functional significance and regulation in the cells remain poorly understood. To investigate the exact bilolgical function of CKII, we have identified proteins that interact with the subunits of CKII using the two-hybrid system. In this report, we have identified cathepsin L, a lysosomal protease, as a cellular protein capable of interacting with the β subunit of CKII. Cathepsin L does not interact with the α subunit of CKII, supporting the idea that the β subunit can mediate the interaction of CKII with target proteins. We have found that cathepsin L has several putative CKII phosphorylation sites including Thr-84, Ser-160, Ser-270, Thr-288, and Ser-301. These data suggest that CKII is a possible protein kinase for cathepsin L phosphorylation.
Bae, Young Seuk,Park, Gye Hwa 생화학분자생물학회 2002 BMB Reports Vol.34 No.1
Both topoisomerase IIα and IIβ east as phosphoproteins in the cells. Recently it was reported that DNA topoisomerase IIa associates with and is phosphorylated by the extracellular signal-regulated kinase 2 (ERK2). Also, ERK2 stimulates the activity of topoisomerase B by a phosphorylation-independent manner [Shapiro et al., (1999) Mol. Cell. Biol. 19, 3551-3560]. In this study, a yeast twohybrid system was used to investigate the binding site between topoisomerase IIα or IIβ and ERK2. The twohybrid test clearly showed that topoisomerase IIβ residues 1099-1263, and topoisomerase IIα residues 1078-1182, mediate the interaction with ERK2, and that the leucine zipper motifs of topoisomerase IIα and IIβ are not required for its physical binding to ERK2. Our results suggest that topoisomerase IIβ residues 1099-1263, and topoisomerase IIα residues 1078-1182, may be common binding sites for activator proteins.
( Young Hoon Lee ),( Jong Su Uhm ),( Soo Hyun Yoon ),( Ji Young Kang ),( Eun Kyung Kim ),( Beom Sik Kang ),( Do Sik Min ),( Young Seuk Bae ) 생화학분자생물학회(구 한국생화학분자생물학회) 2011 BMB Reports Vol.44 No.9
Elevated phospholipase D (PLD) expression prevents cell cycle arrest and apoptosis. However, the roles of PLD isoforms in cell proliferation and apoptosis are incompletely understood. Here, we investigated the physiological significance of the interaction between PLD2 and protein kinase CKII (CKII) in HCT116 human colorectal carcinoma cells. PLD2 interacted with the CKIIβ subunit in HCT116 cells. The C-terminal domain (residues 578-933) of PLD2 and the N-terminal domain of CKIIβ were necessary for interaction between the two proteins. PLD2 relocalized CKIIβ to the plasma membrane area. Overexpression of PLD2 reduced CKIIβ protein level, whereas knockdown of PLD2 led to an increase in CKIIβ expression. PLD2-induced CKIIβ reduction was mediated by ubiquitin-dependent degradation. The C-terminal domain of PLD2 was sufficient for CKIIβ degradation as the catalytic activity of PLD2 was not required. Taken together, the results indicate that the C-terminal domain of PLD2 can regulate CKII by accelerating CKIIβ degradation in HCT116 cells. [BMB reports 2011; 44(9): 572-577]
In Vitro Characterization of Protein Kinase CKII b Mutants Defective in b-b Dimerization
Young-Seuk Bae,Tae-Hyun Kim,Jae-Yong Lee,Beom Sik Kang 한국분자세포생물학회 2005 Molecules and cells Vol.19 No.1
Protein kinase CKII is composed of two catalytic (α orα′) subunits and two regulatory (β) subunits. The β subunit mediates tetramer formation through β-βhomodimerization and α-β eterodimerization. In a previous study R26 and R75, point mutants of CKIIβ defective in β-β dimerization, were isolated. In the present work we characterized these CKIIβ mutants in vitro. Purified R26 and R75 bound to CKIIα but were defective in binding to CKIIβ. R75 stimulated the catalytic activity of CKII whereas R26 gave little stimulation, and poly-L-lysine increased the stimulation of catalytic activity by R26 or R75. Circular dichroism and intrinsic fluorescence data pointed to different conformational changes in R26 and R75. Molecular modeling of these mutants provides an explanation of the difference in their ability to interact withCKIIβ and to activate CKIIα.
Apoptotic cell death of human leukaemia U937 cells by ubiquinone-9 purified from Pleurotus eryngii
Bae, Jeen-Soo,Park, Jin Wook,Park, So Hyun,Park, Jung Bin,Rho, Yoon-Hwa,Ryu, Young Bae,Lee, Kun-Sik,Park, Ki-Hun,Bae, Young-Seuk Taylor Francis 2009 NATURAL PRODUCT RESEARCH Vol.23 No.12
<P> A chloroform extract of the edible mushroom Pleurotus eryngii showed an inhibitory effect on mammalian DNA topoisomerase I. The topoisomerase I inhibitory compound was purified and identified as ubiquinone-9. Ubiquinone-9 was shown to inhibit the activity of topoisomerase I with IC50 of about 50 µM. Concentration of 110 µM ubiquinone-9 caused 50% growth inhibition of human leukaemia U937 cells, but not that of normal fibroblast NIH3T3 and 3Y1 cells. Ubiquinone-9-induced cell death was characterised with the cleavage of poly (ADP-ribose) polymerase and pro-caspase 3. Furthermore, ubiquinone-9 induced the fragmentation of DNA into an apoptotic DNA ladder, indicating that the inhibitor triggered apoptosis. The induction of apoptosis by ubiquinone-9 was also confirmed using flow cytometry analysis. Taken together, these results suggest that ubiquinone-9 may function by inhibiting oncogenic disease, at least in part, through the inhibition of topoisomerase I activity.</P>
Young-Seuk Bae,배영석 한국분자세포생물학회 2019 Molecules and cells Vol.42 No.11
Cellular senescence is an irreversible form of cell cycle arrest. Senescent cells have a unique gene expression profile that is frequently accompanied by senescence-associated heterochromatic foci (SAHFs). Protein kinase CK2 (CK2) downregulation can induce trimethylation of histone H3 Lys 9 (H3K9me3) and SAHFs formation by activating SUV39h1. Here, we present evidence that the PI3K-AKTmTOR-reactive oxygen species-p53 pathway is necessary for CK2 downregulation-mediated H3K9me3 and SAHFs formation. CK2 downregulation promotes SUV39h1 stability by inhibiting its proteasomal degradation in a p53dependent manner. Moreover, the dephosphorylation status of Ser 392 on p53, a possible CK2 target site, enhances the nuclear import and subsequent stabilization of SUV39h1 by inhibiting the interactions between p53, MDM2, and SUV39h1. Furthermore, p21Cip1/WAF1 is required for CK2 downregulation-mediated H3K9me3, and dephosphorylation of Ser 392 on p53 is important for efficient transcription of p21Cip1/WAF1. Taken together, these results suggest that CK2 downregulation induces dephosphorylation of Ser 392 on p53, which subsequently increases the stability of SUV39h1 and the expression of p21Cip1/WAF1, leading to H3K9me3 and SAHFs formation.
Interaction of the β Subunit of Casein Kinase 2 with the Ribosomal Protein L5
Bae, Young Seuk,Kim, Jeong Min,Cha, Ji Young,Marshak, Daniel R . 경북대학교 유전공학연구소 1996 遺傳工學硏究所報 Vol.11 No.1
Casein kinase II (CKII) usually exists as a heterotetramer with α₂β₂, αα'β₂, or α'₂β₂. The α or α' subunits catalyze protein phosphorylation, whereas the function of the β subunit remains unclear. One of the possible functions of the β subunit may be to mediate the interaction of the catalytic subunit with target proteins. To identify proteins capable of associating with the β subunit in vivo, we have used a two-hybrid system. One protein identified is human ribosomal protein L5. The protein L5 does not interact with the α or α' subunits of CKII, supporting the idea that the β subunit can determine a substrate specificity of CKII. These results furthermore suggest a novel role for CKII in ribosomal L5 phosphorylation, in ribosomal assembly, or ribosomal transport in the intact cells. The protein L5 may act as a regulator of the activity or subcellular localization of CKII.