Q37375098
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Smarca5, an ATPase of the ISWI class of chromatin remodelers, is a key regulator of chromatin structure, cell cycle and DNA repair. Smarca5 is deregulated in leukemia and breast, lung and gastric cancers. However, its role in oncogenesis is not well understood. Chromatin remodelers often play dosage-dependent roles in cancer. We therefore investigated the epigenomic and phenotypic impact of controlled stepwise attenuation of Smarca5 function in the context of primary cell transformation, a process relevant to tumor formation. Upon conditional single- or double-allele Smarca5 deletion, the cells underwent both accelerated growth arrest and senescence entry and displayed gradually increased sensitivity to genotoxic insults. These phenotypic characteristics were explained by specific remodeling of the chromatin structure and the transcriptome in primary cells prior to the immortalization onset. These molecular programs implicated Smarca5 requirement in DNA damage repair, telomere maintenance, cell cycle progression and in restricting apoptosis and cellular senescence. Consistent with the molecular programs, we demonstrate for the first time that Smarca5-deficient primary cells exhibit dramatically decreased capacity to bypass senescence and immortalize, an indispensable step during cell transformation and cancer development. Thus, Smarca5 plays a crucial role in key homeostatic processes and sustains cancer-promoting molecular programs and cellular phenotypes.
The oncogenic cluster miR-17-92 encodes seven related microRNAs that regulate cell proliferation, apoptosis and development. Expression of miR-17-92 cluster is decreased upon cell differentiation. Here, we report a novel mechanism of the regulation of miR-17-92 cluster. Using transgenic PU.1(-/-) myeloid progenitors we show that upon macrophage differentiation, the transcription factor PU.1 induces the secondary determinant Egr2 which, in turn, directly represses miR-17-92 expression by recruiting histone demethylase Jarid1b leading to histone H3 lysine K4 demethylation within the CpG island at the miR-17-92 promoter. Conversely, Egr2 itself is targeted by miR-17-92, indicating existence of mutual regulatory relationship between miR-17-92 and Egr2. Furthermore, restoring EGR2 levels in primary acute myeloid leukaemia blasts expressing elevated levels of miR-17-92 and low levels of PU.1 and EGR2 leads to downregulation of miR-17-92 and restored expression of its targets p21CIP1 and BIM. We propose that upon macrophage differentiation PU.1 represses the miR-17-92 cluster promoter by an Egr-2/Jarid1b-mediated H3K4 demethylation mechanism whose deregulation may contribute to leukaemic states.
- MeSH
- biologické modely MeSH
- buněčná diferenciace genetika MeSH
- buňky NIH 3T3 MeSH
- doména Jumonji s histondemethylasami metabolismus fyziologie MeSH
- epigeneze genetická fyziologie MeSH
- HL-60 buňky MeSH
- jaderné proteiny metabolismus fyziologie MeSH
- kultivované buňky MeSH
- lidé MeSH
- makrofágy metabolismus fyziologie MeSH
- mikro RNA genetika metabolismus MeSH
- multigenová rodina genetika MeSH
- myši MeSH
- protein 2 časné růstové odpovědi metabolismus fyziologie MeSH
- protoonkogenní proteiny genetika metabolismus fyziologie MeSH
- represorové proteiny metabolismus fyziologie MeSH
- sekvence nukleotidů MeSH
- sekvenční homologie nukleových kyselin MeSH
- technika přenosu genů MeSH
- trans-aktivátory genetika metabolismus fyziologie MeSH
- transfekce MeSH
- umlčování genů fyziologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- MeSH
- chronická lymfatická leukemie genetika patofyziologie MeSH
- lidé MeSH
- mikro RNA diagnostické užití genetika MeSH
- onkogenní proteiny v-myb diagnostické užití genetika MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- novinové články MeSH
Elevated levels of microRNA miR-155 represent a candidate pathogenic factor in chronic B-lymphocytic leukemia (B-CLL). In this study, we present evidence that MYB (v-myb myeloblastosis viral oncogene homolog) is overexpressed in a subset of B-CLL patients. MYB physically associates with the promoter of miR-155 host gene (MIR155HG, also known as BIC, B-cell integration cluster) and stimulates its transcription. This coincides with the hypermethylated histone H3K4 residue and spread hyperacetylation of H3K9 at MIR155HG promoter. Our data provide evidence of oncogenic activities of MYB in B-CLL that include its stimulatory role in MIR155HG transcription.
- MeSH
- chromatin chemie genetika metabolismus MeSH
- chronická lymfatická leukemie genetika metabolismus MeSH
- genetická transkripce fyziologie MeSH
- HeLa buňky MeSH
- lidé MeSH
- mikro RNA genetika MeSH
- mikročipová analýza MeSH
- nádorové buňky kultivované MeSH
- onkogenní proteiny v-myb metabolismus fyziologie MeSH
- promotorové oblasti (genetika) MeSH
- regulace genové exprese u leukemie MeSH
- shluková analýza MeSH
- stanovení celkové genové exprese MeSH
- transfekce MeSH
- vazba proteinů MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Hematopoietic transcription factors GATA-1 and PU.1 bind each other on DNA to block transcriptional programs of undesired lineage during hematopoietic commitment. Murine erythroleukemia (MEL) cells that coexpress GATA-1 and PU.1 are blocked at the blast stage but respond to molecular removal (downregulation) of PU.1 or addition (upregulation) of GATA-1 by inducing terminal erythroid differentiation. To test whether GATA-1 blocks PU.1 in MEL cells, we have conditionally activated a transgenic PU.1 protein fused with the estrogen receptor ligand-binding domain (PUER), resulting in activation of a myeloid transcriptional program. Gene expression arrays identified components of the PU.1-dependent transcriptome negatively regulated by GATA-1 in MEL cells, including CCAAT/enhancer binding protein alpha (Cebpa) and core-binding factor, beta subunit (Cbfb), which encode two key hematopoietic transcription factors. Inhibition of GATA-1 by small interfering RNA resulted in derepression of PU.1 target genes. Chromatin immunoprecipitation and reporter assays identified PU.1 motif sequences near Cebpa and Cbfb that are co-occupied by PU.1 and GATA-1 in the leukemic blasts. Significant derepression of Cebpa and Cbfb is achieved in MEL cells by either activation of PU.1 or knockdown of GATA-1. Furthermore, transcriptional regulation of these loci by manipulating the levels of PU.1 and GATA-1 involves quantitative increases in a transcriptionally active chromatin mark: acetylation of histone H3K9. Collectively, we show that either activation of PU.1 or inhibition of GATA-1 efficiently reverses the transcriptional block imposed by GATA-1 and leads to the activation of a myeloid transcriptional program directed by PU.1.
- MeSH
- aktivace transkripce genetika MeSH
- buněčná diferenciace genetika MeSH
- HeLa buňky MeSH
- histony genetika metabolismus MeSH
- leukemie genetika metabolismus patofyziologie MeSH
- lidé MeSH
- malá interferující RNA MeSH
- myeloidní buňky metabolismus MeSH
- nádorová transformace buněk genetika metabolismus MeSH
- protein CBFB genetika metabolismus MeSH
- proteiny vázající zesilovač transkripce CCAAT genetika metabolismus MeSH
- protoonkogenní proteiny genetika MeSH
- regulace genové exprese u nádorů genetika MeSH
- regulační elementy transkripční genetika MeSH
- rekombinantní fúzní proteiny genetika metabolismus MeSH
- represorové proteiny genetika metabolismus MeSH
- RNA interference MeSH
- trans-aktivátory genetika MeSH
- transkripční faktor GATA1 genetika metabolismus MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH