Histone modifications: combinatorial complexity or cumulative simplicity?

To test our hypothesis that proatherogenic lysophosphatidylcholine (LPC) upregulates trained immunity pathways (TIPs) in human aortic endothelial cells (HAECs), we conducted an intensive analyses on our RNA-Seq data and histone 3 lysine 14 acetylation (H3K14ac)-CHIP-Seq data, both performed on HAEC treated with LPC. Our analysis revealed that: 1) LPC induces upregulation of three TIPs including glycolysis enzymes (GE), mevalonate enzymes (ME), and acetyl-CoA generating enzymes (ACE); 2) LPC induces upregulation of 29% of 31 histone acetyltransferases, three of which acetylate H3K14; 3) LPC induces H3K14 acetylation (H3K14ac) in the genomic DNA that encodes LPC-induced TIP genes (79%) in comparison to that of in LPC-induced effector genes (43%) including ICAM-1; 4) TIP pathways are significantly different from that of EC activation effectors including adhesion molecule ICAM-1; 5) reactive oxygen species generating enzyme NOX2 deficiency decreases, but antioxidant transcription factor Nrf2 deficiency increases, the expressions of a few TIP genes and EC activation effector genes; and 6) LPC induced TIP genes(81%) favor inter-chromosomal long-range interactions (CLRI, trans-chromatin interaction) while LPC induced effector genes (65%) favor intra-chromosomal CLRIs (cis-chromatin interaction). Our findings demonstrated that proatherogenic lipids upregulate TIPs in HAECs, which are a new category of qualification markers for chronic disease risk factors and conditional DAMPs and potential mechanisms for acute inflammation transition to chronic ones. These novel insights may lead to identifications of new cardiovascular risk factors in upregulating TIPs in cardiovascular cells and novel therapeutic targets for the treatment of metabolic cardiovascular diseases, inflammation, and cancers. (total words: 245).

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PubMed2006

Loss of interleukin-2-dependency in HTLV-I-infected T cells on gene silencing of thioredoxin-binding protein-2.

The transition from interleukin-2 (IL-2)-dependent to IL-2-independent growth is considered one of the key steps in the transformation of human T-cell leukemia virus type-I (HTLV-I)-infected T cells. The expression of thioredoxin-binding protein-2 (TBP-2) is lost during the transition of HTLV-I-infected T-cell lines. Here, we analysed the mechanism of loss of TBP-2 expression and the role of TBP-2 in IL-2-dependent growth in the in vitro model to investigate multistep transformation of HTLV-I. CpGs in the TBP-2 gene are methylated in IL-2-independent but not in IL-2-dependent cells. Sequential treatment with 5-aza-2'-deoxycytidine and a histone deacetylase inhibitor augmented histone acetylation and TBP-2 expression, suggesting that loss of TBP-2 expression is due to DNA methylation and histone deacetylation. In IL-2-dependent cells, a basal level of TBP-2 expression was maintained by IL-2 associated with cellular growth, whereas TBP-2 expression was upregulated on deprivation of IL-2 associated with growth suppression. Overexpression of TBP-2 in IL-2-independent cells suppressed the growth and partially restored responsiveness to IL-2. Knockdown of TBP-2 caused the IL-2-dependent cells to show partial growth without IL-2. These results suggested that epigenetic silencing of the TBP-2 gene results in a loss of responsiveness to IL-2, contributing to uncontrolled IL-2-independent growth in HTLV-I-infected T-cell lines.

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PubMed2006

Cell growth-dependent subcellular localization of p8.

p8 is a stress-induced protein, biochemically related to the architectural factor HMG-I/Y, overexpressed in many cancers and required for tumor expansion. The molecular mechanisms by which p8 may exert its effect in aspects of growth is unknown. Using immunocytochemistry, we found that p8 presents nuclear localization in sub-confluent cells, but it localizes throughout the whole cell in high density grown cells. Cells arrested in Go/G1, either by serum deprivation or by hydroxyurea treatment, show a nucleo-cytoplasmic localization of p8, whether in the rest of the cell cycle stages of actively dividing cells the localization is nuclear. A comparison of p8 sequences from human to fly predicts a conserved bipartite nuclear localization sequence (NLS). The putative NLS has been demonstrated to be functional, since nuclear import is energy dependent (inhibited by sodium azide plus 2-deoxyglucose), and fusion proteins GFP-p8 and GFP-NLSp8 localize to the nucleus, whereas GFP-p8NLSmut in which with Lys 65, 69, 76, and 77 mutated to Ala localized to the whole cell. p8 localization does not involve the CRM1 transporter, since it is insensitive to leptomycin B. Inhibitors of MAPK pathways did not affect p8 subcellular localization. The inhibition of deacetylation with Trichostatin A promotes cytoplasmic accumulation of p8. The results suggest that p8 growth stage-dependent localization is regulated by acetylation, that p8 is not free within the cell but forming part of a complex and that it may exert a role in both subcellular localizations.

Acetylation↗