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Downregulation of bcl - xL Is Relevant to UV - induced Apoptosis in Fibroblasts
(Yuki Nakagawa),(Seiji Okada),(Masahiko Hatano),(Masaaki Ebara),(Hiromitsu Saisho),(Takeshi Tokuhisa) 생화학분자생물학회 2002 BMB Reports Vol.35 No.5
Exposure to ultraviolet light (UV) induces apoptosis in mammalian cells. The caspase group of proteases is required for the apoptosis. This pathway is initiated by a release of cytochrome c from the mitochondria into the cytosol. Several Bcl-2 family proteins can regulate the release of cytochrome c by stabilizing the mitochondrial membrane. Here we show that expression of the endogenous bcl-xL was strongly downregulated in NIH3T3 cells within 2 h after UV-C irradiation, and that of bax was upregulated from 8 h after irradiation. Apoptosis was induced in more than 50% of the NIH3T3 cells 48 h after irradiation. Constitutive overexpression of bcl-xL in NIH3T3 cells protected the UV-induced apoptosis by preventing the loss of mitochondrial membrane potential and the activation of caspase 9. These results suggest that downregulation of Bcl-xL is relevant to UV-induced apoptosis of fibroblasts.
Downregulation of bcl-xL Is Relevant to UV-induced Apoptosis in Fibroblasts
Nakagawa, Yuki,Okada, Seiji,Hatano, Masahiko,Ebara, Masaaki,Saisho, Hiromitsu,Tokuhisa, Takeshi Korean Society for Biochemistry and Molecular Biol 2002 Journal of biochemistry and molecular biology Vol.35 No.5
Exposure to ultraviolet light (UV) induces apoptosis in mammalian cells, The caspase group of proteases is required for the appotosis. This pathway is initiated by a release of cytochrome c from the mitochondria into the cytosol. Several Bcl-2 family proteins can regulate the release of cytochrome c by stabilizing the mitochondrial membrane. Here we show that expression of the endogenous bcl-xL was strongly downregulated in NIH3T3 cells within 2 h after UV-C irradiation, and that of bax was upregulated from 8 h after irradiation. Apoptosis was induced in more than 50% of the NIH3T3 cells 48 h after irradiation. Constitutive overexpression of bcl-xL in NIH3T3 cells protected the UV-induced apoptosis by preventing the loss of mitochondrial membrane potential and the activation of caspase 9. There results suggest that downregulation of Bcl-xL is relevant to UV-induced apoptosis of tibroblasts.
Kim, Min-Kyeong,Song, Ji-Yang,Koh, Dong-In,Kim, Jin Young,Hatano, Masahiko,Jeon, Bu-Nam,Kim, Min-Young,Cho, Su-Yeon,Kim, Kyung-Sup,Hur, Man-Wook American Society for Biochemistry and Molecular Bi 2019 The Journal of biological chemistry Vol.294 No.1
<P>Even in the face of physiological DNA damage or expression of the tumor suppressor protein p53, B cell CLL/lymphoma 6 (BCL6) increases proliferation and antagonizes apoptotic responses in B cells. BCL6 represses <I>TP53</I> transcription and also appears to inactivate p53 at the protein level, and additional findings have suggested negative mutual regulation between BCL6 and p53. Here, using <I>Bcl6</I><SUP>−/−</SUP> knockout mice, HEK293A and HCT116 <I>p53</I><SUP>−/−</SUP> cells, and site-directed mutagenesis, we found that BCL6 interacts with p53 and thereby inhibits acetylation of Lys-132 in p53 by E1A-binding protein p300 (p300), a modification that normally occurs upon DNA damage–induced cellular stress and whose abrogation by BCL6 diminished transcriptional activation of p53 target genes, including that encoding caspase-1. Conversely, we also found that BCL6 protein is degraded via p53-induced, caspase-mediated proteolytic cleavage, and the formation of a BCL6–p53–caspase-1 complex. Our results suggest that p53 may block oncogenic transformation by decreasing BCL6 stability via caspase-1 up-regulation, whereas aberrant BCL6 expression inactivates transactivation of p53 target genes, either by inhibiting p53 acetylation by p300 or repressing <I>TP53</I> gene transcription. These findings have implications for B cell development and lymphomagenesis.</P>