Yeast mtDNA is compacted into nucleoprotein structures called mitochondrial nucleoids (mt-nucleoids). The principal mediators of nucleoid formation are mitochondrial high-mobility group (HMG)-box containing (mtHMG) proteins. Although these proteins are some of the fastest evolving components of mt-nucleoids, it is not known whether the divergence of mtHMG proteins on the level of their amino acid sequences is accompanied by diversification of their biochemical properties. In the present study we performed a comparative biochemical analysis of yeast mtHMG proteins from Saccharomyces cerevisiae (ScAbf2p), Yarrowia lipolytica (YlMhb1p) and Candida parapsilosis (CpGcf1p). We found that all three proteins exhibit relatively weak binding to intact dsDNA. In fact, ScAbf2p and YlMhb1p bind quantitatively to this substrate only at very high protein to DNA ratios and CpGcf1p shows only negligible binding to dsDNA. In contrast, the proteins exhibit much higher preference for recombination intermediates such as Holliday junctions (HJ) and replication forks (RF). Therefore, we hypothesize that the roles of the yeast mtHMG proteins in maintenance and compaction of mtDNA in vivo are in large part mediated by their binding to recombination/replication intermediates. We also speculate that the distinct biochemical properties of CpGcf1p may represent one of the prerequisites for frequent evolutionary tinkering with the form of the mitochondrial genome in the CTG-clade of hemiascomycetous yeast species.

• Klíčová slova
• DNA compaction, DNA-binding protein, HMG-box containing protein, Holliday junction, mitochondrial DNA (mtDNA), mitochondrial nucleoid,
• MeSH
• Candida genetika   metabolismus   MeSH
• mitochondriální proteiny genetika   metabolismus   MeSH
• molekulární evoluce * MeSH
• proteiny s vysokou pohyblivostí genetika   metabolismus   MeSH
• Saccharomyces cerevisiae - proteiny genetika   metabolismus   MeSH
• Saccharomyces cerevisiae genetika   metabolismus   MeSH
• Yarrowia genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• mitochondriální proteiny MeSH
• proteiny s vysokou pohyblivostí MeSH
• Saccharomyces cerevisiae - proteiny MeSH

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

Topoisomerase IIalpha (topo IIalpha) is a nuclear enzyme involved in several critical processes, including chromosome replication, segregation and recombination. Previously we have shown that chromosomal protein HMGB1 interacts with topo IIalpha, and stimulates its catalytic activity. Here we show the effect of HMGB1 on the activity of the human topo IIalpha gene promoter in different cell lines. We demonstrate that HMGB1, but not a mutant of HMGB1 incapable of DNA bending, up-regulates the activity of the topo IIalpha promoter in human cells that lack functional retinoblastoma protein pRb. Transient over-expression of pRb in pRb-negative Saos-2 cells inhibits the ability of HMGB1 to activate the topo IIalpha promoter. The involvement of HMGB1 and its close relative, HMGB2, in modulation of activity of the topo IIalpha gene is further supported by knock-down of HMGB1/2, as evidenced by significantly decreased levels of topo IIalpha mRNA and protein. Our experiments suggest a mechanism of up-regulation of cellular expression of topo IIalpha by HMGB1/2 in pRb-negative cells by modulation of binding of transcription factor NF-Y to the topo IIalpha promoter, and the results are discussed in the framework of previously observed pRb-inactivation, and increased levels of HMGB1/2 and topo IIalpha in tumors.

• MeSH
• aktivace transkripce MeSH
• antigeny nádorové biosyntéza   genetika   MeSH
• DNA vazebné proteiny biosyntéza   genetika   MeSH
• DNA-topoisomerasy typu II biosyntéza   genetika   MeSH
• DNA chemie   metabolismus   MeSH
• faktor vázající CCAAT metabolismus   MeSH
• lidé MeSH
• mutageneze MeSH
• nádorové buněčné linie MeSH
• promotorové oblasti (genetika) MeSH
• protein HMGB1 chemie   genetika   metabolismus   MeSH
• protein HMGB2 metabolismus   MeSH
• retinoblastomový protein metabolismus   MeSH
• senioři MeSH
• upregulace * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antigeny nádorové MeSH
• DNA vazebné proteiny MeSH
• DNA-topoisomerasy typu II MeSH
• DNA MeSH
• faktor vázající CCAAT MeSH
• protein HMGB1 MeSH
• protein HMGB2 MeSH
• retinoblastomový protein MeSH

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