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

Telomere homeostasis is regulated at multiple levels, including the local chromatin structure of telomeres and subtelomeres. Recent reports demonstrated that a decrease in repressive chromatin marks, such as levels of cytosine methylation in subtelomeric regions, results in telomere elongation in mouse cells. Here we show that a considerable fraction of cytosines is methylated not only in subtelomeric, but also in telomeric DNA of tobacco BY-2 cells. Drug-induced hypomethylation (demonstrated at subtelomeric, telomeric, and global DNA levels) results in activation of telomerase. However, in contrast to mouse cells, the decrease in 5-methylcytosine levels and upregulation of telomerase do not result in any changes of telomere lengths. These results demonstrate the involvement of epigenetic mechanisms in the multilevel process of regulation of telomerase activity in plant cells and, at the same time, they indicate that changes in telomerase activity can be overridden by other factors governing telomere length stability.

• MeSH
• adenin analogy a deriváty   farmakologie   MeSH
• aktivace enzymů účinky léků   MeSH
• cytidin analogy a deriváty   farmakologie   MeSH
• DNA rostlinná chemie   účinky léků   MeSH
• epigeneze genetická MeSH
• genetická transkripce účinky léků   MeSH
• kultivované buňky MeSH
• metylace DNA účinky léků   MeSH
• nukleozomy účinky léků   fyziologie   MeSH
• rostlinné proteiny genetika   metabolismus   MeSH
• tabák cytologie   účinky léků   genetika   metabolismus   MeSH
• telomerasa metabolismus   MeSH
• telomery chemie   účinky léků   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 9-(2,3-dihydroxypropyl)adenine MeSH Prohlížeč
• adenin MeSH
• cytidin MeSH
• DNA rostlinná MeSH
• nukleozomy MeSH
• pyrimidin-2-one beta-ribofuranoside MeSH Prohlížeč
• rostlinné proteiny MeSH
• telomerasa MeSH