HMGB1 protein and linker histone H1 have overlapping binding sites in the nucleosome. HMGB1 has been implicated in many DNA-dependent processes in chromatin involving binding of specific proteins, including transcription factors, to DNA sites pre-bent by HMGB1. HMGB1 can also act as an extracellular signaling molecule by promoting inflammation, tumor growth a metastasis. Many of the intra- and extracellular functions of HMGB1 depend on redox-sensitive cysteine residues of the protein. Here we report that mild oxidization of HMGB1 (and much less mutation of cysteines involved in disulphide bond formation) can severely compromise the functioning of the protein as a DNA chaperone by inhibiting its ability to unwind or bend DNA. Histone H1 (via the highly basic C-terminal domain) significantly inhibits DNA bending by the full-length HMGB1, and the inhibition is further enhanced upon oxidization of HMGB1. Interestingly, DNA bending by HMGB1 lacking the acidic C-tail (HMGB1ΔC) is much less affected by histone H1, but oxidization rendered DNA bending by HMGB1ΔC and HMGB1 equally prone for inhibition by histone H1. Possible consequences of histone H1-mediated inhibition of DNA bending by HMGB1 of different redox state for the functioning of chromatin are discussed.

• MeSH
• cystein genetika   metabolismus   MeSH
• histony chemie   genetika   metabolismus   MeSH
• krysa rodu Rattus MeSH
• molekulární modely MeSH
• mutace MeSH
• nukleozomy MeSH
• oxidace-redukce MeSH
• protein HMGB1 chemie   genetika   metabolismus   MeSH
• superhelikální DNA metabolismus   MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cystein MeSH
• Hbp1 protein, rat MeSH Prohlížeč
• histony MeSH
• nukleozomy MeSH
• protein HMGB1 MeSH
• superhelikální DNA MeSH

HMGB1 is an architectural protein in chromatin, acting also as a signaling molecule outside the cell. Recent reports from several laboratories provided evidence that a number of both the intracellular and extracellular functions of HMGB1 may depend on redox-sensitive cysteine residues of the protein. In this study we demonstrate that redox state of HMGB1 can significantly modulate the ability of the protein to bind and bend DNA, as well as to promote DNA end-joining. We also report a high affinity binding of histone H1 to hemicatenated DNA loops and DNA minicircles. Finally, we show that reduced HMGB1 can readily displace histone H1 from DNA, while oxidized HMGB1 has limited capacity for H1 displacement. Our results suggested a novel mechanism for the HMGB1-mediated modulation of histone H1 binding to DNA. Possible biological consequences of linker histones H1 replacement by HMGB1 for the functioning of chromatin are discussed.

• MeSH
• chromatin genetika   metabolismus   MeSH
• exprese genu MeSH
• genetické vektory chemie   MeSH
• histony genetika   metabolismus   MeSH
• konkatenovaná DNA genetika   metabolismus   MeSH
• kruhová DNA genetika   metabolismus   MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• oxidace-redukce MeSH
• protein HMGB1 genetika   metabolismus   MeSH
• rekombinantní proteiny genetika   metabolismus   MeSH
• skot MeSH
• vazba proteinů MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• skot MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromatin MeSH
• histony MeSH
• konkatenovaná DNA MeSH
• kruhová DNA MeSH
• protein HMGB1 MeSH
• rekombinantní proteiny MeSH

Telomere repeats are added onto chromosome ends by telomerase, consisting of two main core components: a catalytic protein subunit (telomerase reverse trancriptase, TERT), and an RNA subunit (telomerase RNA, TR). Here, we report for the first time evidence that HMGB1 (a chromatin-associated protein in mammals, acting as a DNA chaperone in transcription, replication, recombination, and repair) can modulate cellular activity of mammalian telomerase. Knockout of the HMGB1 gene (HMGB1 KO) in mouse embryonic fibroblasts (MEFs) results in chromosomal abnormalities, enhanced colocalization of γ-H2AX foci at telomeres, and a moderate shortening of telomere lengths. HMGB1 KO MEFs also exhibit significantly (>5-fold) lower telomerase activity than the wild-type MEFs. Correspondingly, enhanced telomerase activity is observed upon overexpression of HMGB1 in MEFs. HMGB1 physically interacts with both TERT and TR, as well as with active telomerase complex in vitro. However, direct interaction of HMGB1 with telomerase is most likely not accountable for the observed higher telomerase activity in HMGB1-containing cells, as revealed from the inability of purified HMGB1 protein to stimulate telomerase activity in vitro. While no transcriptional silencing of TERT is observed in HMGB1 KO MEFs, levels of TR are diminished (~3-fold), providing possible explanation for the observed lower telomerase activity in HMGB1 KO cells. Interestingly, knockout of the HMGB2 gene elevates telomerase activity (~3-fold) in MEFs, suggesting that the two closely related proteins of the HMGB family, HMGB1 and HMGB2, have opposite effects on telomerase activity in the cell. The ability of HMGB1 to modulate cellular activity of telomerase and to maintain telomere integrity can help to understand some aspects of the protein involvement in chromosome stability and cancer.

• MeSH
• buněčné linie MeSH
• chromozomální aberace MeSH
• down regulace MeSH
• fibroblasty cytologie   metabolismus   MeSH
• fluorescenční mikroskopie MeSH
• fragmentace DNA MeSH
• genový knockout * MeSH
• histony genetika   metabolismus   MeSH
• hybridizace in situ fluorescenční MeSH
• myši MeSH
• poškození DNA MeSH
• protein HMGB1 genetika   metabolismus   MeSH
• protein HMGB2 genetika   metabolismus   MeSH
• replikace DNA MeSH
• RNA genetika   metabolismus   MeSH
• telomerasa genetika   metabolismus   MeSH
• telomery metabolismus   patologie   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• gamma-H2AX protein, mouse MeSH Prohlížeč
• histony MeSH
• protein HMGB1 MeSH
• protein HMGB2 MeSH
• RNA MeSH
• telomerasa MeSH
• telomerase RNA MeSH Prohlížeč
• Tert protein, mouse MeSH Prohlížeč

DNA topoisomerase IIalpha (topo IIalpha) is an essential nuclear enzyme and its unique decatenation activity has been implicated in many aspects of chromosome dynamics such as chromosome replication and segregation during mitosis. Here we show that chromatin-associated protein HMGB1 (a member of the large family of HMG-box proteins with possible functions in DNA replication, transcription, recombination and DNA repair) promotes topo IIalpha-mediated catenation of circular DNA, relaxation of negatively supercoiled DNA and decatenation of kinetoplast DNA. HMGB1 interacts with topo IIalpha and this interaction, like the stimulation of the catalytic activity of the enzyme, requires both HMG-box domains of HMGB1. A mutant of HMGB1, which cannot change DNA topology stimulates DNA decatenation by topo IIalpha indistinguishably from the wild-type protein. Although HMGB1 stimulates ATP hydrolysis by topo IIalpha, the DNA cleavage is much more enhanced. The observed abilities of HMGB1 to interact with topo IIalpha and promote topo IIalpha binding to DNA suggest a mechanism by which HMGB1 stimulates the catalytic activity of the enzyme via enhancement of DNA cleavage.

• MeSH
• adenosintrifosfát metabolismus   MeSH
• antigeny nádorové metabolismus   MeSH
• diketopiperaziny MeSH
• DNA vazebné proteiny metabolismus   MeSH
• DNA-topoisomerasy typu II metabolismus   MeSH
• DNA chemie   metabolismus   ultrastruktura   MeSH
• elektroforéza v agarovém gelu MeSH
• inhibitory enzymů farmakologie   MeSH
• katalýza MeSH
• kinetoplastová DNA metabolismus   MeSH
• konformace nukleové kyseliny MeSH
• kruhová DNA metabolismus   MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• piperaziny farmakologie   MeSH
• protein HMGB1 MeSH
• proteiny s vysokou pohyblivostí metabolismus   MeSH
• represorové proteiny metabolismus   MeSH
• superhelikální DNA metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione MeSH Prohlížeč
• adenosintrifosfát MeSH
• antigeny nádorové MeSH
• diketopiperaziny MeSH
• DNA vazebné proteiny MeSH
• DNA-topoisomerasy typu II MeSH
• DNA MeSH
• Hbp1 protein, rat MeSH Prohlížeč
• inhibitory enzymů MeSH
• kinetoplastová DNA MeSH
• kruhová DNA MeSH
• piperaziny MeSH
• protein HMGB1 MeSH
• proteiny s vysokou pohyblivostí MeSH
• represorové proteiny MeSH
• superhelikální DNA MeSH