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  • 1
    Keywords: CANCER ; CELLS ; transcription ; MOUSE ; ORGANIZATION ; SATELLITE REPEATS ; CTCF ; HISTONE ; CCCTC-BINDING FACTOR ; TRIMETHYLATION
    Abstract: Cohesin plays an important role in chromatid cohesion and has additional functions in higher-order chromatin organization and in transcriptional regulation. The binding of cohesin to euchromatic regions is largely mediated by CTCF or the mediator complex. However, it is currently unknown how cohesin is recruited to pericentric heterochromatin in mammalian cells. Here we define the histone methyltransferase Suv4-20h2 as a major structural constituent of heterochromatin that mediates chromatin compaction and cohesin recruitment. Suv4-20h2 stably associates with pericentric heterochromatin through synergistic interactions with multiple heterochromatin protein 1 (HP1) molecules, resulting in compaction of heterochromatic regions. Suv4-20h mutant cells display an overall reduced chromatin compaction and an altered chromocenter organization in interphase referred to as "chromocenter scattering." We found that Suv4-20h-deficient cells display chromosome segregation defects during mitosis that coincide with reduced sister chromatid cohesion. Notably, cohesin subunits interact with Suv4-20h2 both in vitro and in vivo. This interaction is necessary for cohesin binding to heterochromatin, as Suv4-20h mutant cells display substantially reduced cohesin levels at pericentric heterochromatin. This defect is most prominent in G0-phase cells, where cohesin is virtually lost from heterochromatin, suggesting that Suv4-20h2 is involved in the initial loading or maintenance of cohesion subunits. In summary, our data provide the first compelling evidence that Suv4-20h2 plays essential roles in regulating nuclear architecture and ensuring proper chromosome segregation.
    Type of Publication: Journal article published
    PubMed ID: 23599346
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  • 2
    Keywords: CELLS ; DIFFERENTIATION ; ELEMENTS ; RECRUITMENT ; HETEROCHROMATIN FORMATION ; NUCLEOSOME ; RIBOSOMAL-RNA GENES ; chromatin compaction ; LANDSCAPE ; L1 RETROTRANSPOSITION
    Abstract: A complex network of regulatory pathways links transcription to cell growth and proliferation. Here we show that cellular quiescence alters chromatin structure by promoting trimethylation of histone H4 at lysine 20 (H4K20me3). In contrast to pericentric or telomeric regions, recruitment of the H4K20 methyltransferase Suv4-20h2 to rRNA genes and IAP elements requires neither trimethylation of H3K9 nor interaction with HP1 proteins but depends on long noncoding RNAs (lncRNAs) that interact with Suv4-20h2. Growth factor deprivation and terminal differentiation lead to upregulation of these lncRNAs, increase in H4K20me3, and chromatin compaction. The results uncover a lncRNA-mediated mechanism that guides Suv4-20h2 to specific genomic loci to establish a more compact chromatin structure in growth-arrested cells.
    Type of Publication: Journal article published
    PubMed ID: 24768537
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  • 3
    ISSN: 1573-904X
    Keywords: capillary zone electrophoresis ; high performance liquid chromatography ; isotachophoresis ; mass spectrometry ; proteins ; degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Capillary zone electrophoresis with isotachophoretic sample preconcentration (ITP-CZE) and reversed-phase high performance liquid chromatography (RP-HPLC) with UV detection and on-line coupling to electrospray-ionization mass spectrometry were investigated for their potential to separate and identify fragments of recombinant human interleukin-6 formed during acidic stress of the parent protein. Results. Based on the orthogonal separation principles governing ITP-CZE and RP-HPLC, different peak patterns were observed using both methods. The selectivity of ESI-MS allowed identification of several co-migrating compounds. Data obtained by on-line ESI-MS were compared to results from off-line investigations by MALDI-TOF-MS performed with single fractions collected from the RP-HPLC system. Cleavage of the protein backbone occurred preferably at acid-labile Asp-sites. The total amount of rhIL-6 needed for ITP-CZE-ESI-MS identification of all fragments was only in the upper femtomole range, while RP-HPLC required amounts of protein three orders of magnitude higher. On the other hand, the low CE sample volume opposes the collection of fractions to perform off-line analysis. Conclusions. Growing acceptance of CE with on-line MS detection for pharmaceutical quality control of proteins is expected.
    Type of Medium: Electronic Resource
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