The differentiation of monocytes into macrophages and dendritic cells involves mechanisms for activation of the innate immune system in response to inflammatory stimuli, such as pathogen infection and environmental cues. Epigenetic reprogramming is thought to play an important role during monocyte differentiation. Complementary to cell surface markers, the characterization of monocytic cell lineages by mass spectrometry based protein/histone expression profiling opens a new avenue for studying immune cell differentiation. Here, we report the application of mass spectrometry and bioinformatics to identify changes in human monocytes during their differentiation into macrophages and dendritic cells. Our data show that linker histone H1 proteins are significantly down-regulated during monocyte differentiation. Although highly enriched H3K9-methyl/S10-phos/K14-acetyl tri-modification forms of histone H3 were identified in monocytes and macrophages, they were dramatically reduced in dendritic cells. In contrast, histone H4 K16 acetylation was found to be markedly higher in dendritic cells than in monocytes and macrophages. We also found that global hyperacetylation generated by the nonspecific histone deacetylase HDAC inhibitor Apicidin induces monocyte differentiation. Together, our data suggest that specific regulation of inter- and intra-histone modifications including H3 K9 methylation, H3 S10 phosphorylation, H3 K14 acetylation, and H4 K16 acetylation must occur in concert with chromatin remodeling by linker histones for cell cycle progression and differentiation of human myeloid cells into macrophages and dendritic cells.The linker histone H1s “beads-on-a-string” structure aids chromatin folding into highly compacted 30 nm chromatin fibers (1). Previous studies demonstrated that histone H1s are differentially expressed and incorporated into chromatin during embryonic stem cell differentiation and reprogramming to pluripotency (2). More than being accumulated after differentiation, the three histone H1 isoforms, H1.3, H1.4, and H1.5, are required for embryonic stem cell differentiation as demonstrated by in vivo H1.3/H1.4/H1.5 triple null experiments (3). Histone H1 null cells exhibit altered nucleosome architecture (4) which may cause epigenetic reprogramming (2), specific changes in gene regulation including repression of pluripotency gene Oct4 expression (3, 5), and cell growth (6, 7). In human blood or bone marrow, hematopoietic stem cells give rise to two major pluripotent progenitor cell lineages, myeloid and lymphoid progenitors, from which are derived mature blood cells including erythrocytes, megakaryocytes, and cells of the myeloid and lymphoid lineages. However, epigenetic regulation or reprogramming in this complex differentiation system has not yet been fully understood. As a follow up to our proteomics studies on epigenetic networks in U937 cell differentiation (8), we have performed proteomics studies on primary human monocyte differentiation. In this report, using proteomics and bioinformatics tools in lieu of microarray analysis of gene expression, we describe the presence of unique protein expression profiles, specifically the linker histones, in monocyte differentiation into macrophages and dendritic cells.Differentiation of monocytes from primary leukemia cell lines or from human peripheral blood mononuclear cells into macrophages or macrophage-like cells using different differentiating reagents has been frequently used as a mimic model for understanding the process of innate and adaptive immune responses to inflammatory stimuli, viral infection, and environmental cues. Either phorbol myristate acetate (PMA)1 or granulocyte-macrophage colony-stimulating factor (GMCSF) has normally been used for differentiation of monocytes, though the former is generally for differentiation of primary monocytic cell lines, while the latter for differentiation of human blood monocytes (9–11). In our experiments, CD14+ monocytes were treated with PMA, PMA + ionomycin, GMCSF, or GMCSF + IL4. After treatment, monocyte differentiation into macrophages or dendritic cells was monitored by mass spectrometry and bioinformatics analyses. We report here that monocytic cell lineages can be distinguished based on protein expression profiles, specifically, histone H1.4 and H1.5 expression patterns. We identified H3K9-methyl/S10-phos/K14-acetyl tri-modification forms in the monocyte and macrophages but not in dendritic cells. In addition, histone H4 K16 acetylation was low in monocytes and macrophages but significantly higher in dendritic cells. Our findings suggest a switch from H3 tri-modification and linker histone expression to histone H4 K16 acetylation occurs during the monocyte-to-dendritic cell transition. 相似文献
Exercise has been regarded as an effective rehabilitation strategy to facilitate motor and cognitive functional recovery after stroke, even though the complex effects associated with exercise-induced repair of cerebral ischemic injury are not fully elucidated. The enhancement of angiogenesis and neurogenesis, and the improvement of synaptic plasticity following moderate exercise are conducive to functional recovery after ischemic damage. Our previous studies have confirmed the angiogenesis and neurogenesis through the caveolin-1/VEGF pathway in MCAO rats. As an essential neurotrophic factor, BDNF has multiple effects on ischemic injury. In this study, we attempted to determine an additional mechanism of treadmill exercise-mediated motor and cognitive functional recovery through the caveolin-1/VEGF pathway associated with BDNF in the ischemic penumbra of MCAO mice. We found that mice exposed to treadmill exercise after the MCAO operation showed a significant up-regulation in expression of caveolin-1, VEGF, BDNF, synapsin I and CYFIP1 proteins, numbers of cells positive for BrdU/CD34, BDNF, BrdU/NeuN, BrdU/Synapsin I and CYFIP1 expression were increased, which support the reduction in neurological deficit and infarction volume, as well as improved synaptic morphology and spatial learning abilities, compared with the non-exercise mice. However, the caveolin-1 inhibitor, daidzein, resulted in increase in neurological deficit and infarction volume. The selective VEGFR2 inhibitor, PD173074, significantly induced larger infarction volume and neurological injury, and decreased the expression of BDNF in the ischemic penumbra. These findings indicate that exercise improves angiogenesis, neurogenesis and synaptic plasticity to ameliorate motor and cognitive impairment after stroke partially through the caveolin-1/VEGF pathway, which is associated with the coregulator factor, BDNF.
Following the 2006 outbreaks of the highly pathogenic porcine reproductive and respiratory syndrome, the causative agent was identified as the highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV). To investigate whether the HP-PRRSV variant continues circulating and accelerating evolution, we sequenced and analyzed the complete genome of the identified HP-PRRSV field strain SD16. The sequence data indicate that the HP-PRRSV variant continues to prevail and accelerate evolution, especially in the nonstructural protein. 相似文献
At telomeric heterochromatin in yeast, the Sir protein complex spreads from Rap1 sites to silence adjacent genes. This cascade is believed to occur when Sir2, an NAD(+)-dependent enzyme, deacetylates histone H3 and H4 N termini, in particular histone H4 K16, enabling more Sir protein binding. Lysine 56 of histone H3 is located at the entry-exit points of the DNA superhelix surrounding the nucleosome, where it may control DNA compaction. We have found that K56 substitutions disrupt silencing severely without decreasing Sir protein binding at the telomere. Our in vitro and in vivo data indicate that Sir2 deacetylates K56 directly in telomeric heterochromatin to compact chromatin and prevent access to RNA polymerase and ectopic bacterial dam methylase. Since the spread of Sir proteins is necessary but not sufficient for silencing, we propose that silencing occurs when Sir2 deacetylates H3 K56 to close the nucleosomal entry-exit gates, enabling compaction of heterochromatin. 相似文献
PPARγ2 is expressed almost exclusively in adipose tissue and plays a central role in adipogenesis. Despite intensive studies over the last 2 decades, the mechanism regulating the expression of the Pparg2 gene, especially the role of cis-regulatory elements, is still not completely understood. Here, we report a comprehensive investigation of the enhancer elements within the murine Pparg2 gene. Utilizing the combined techniques of sequence conservation analysis and chromatin marker examination, we identified a potent enhancer element that augmented the expression of a reporter gene under the control of the Pparg2 promoter by 20-fold. This enhancer element was first identified as highly conserved non-coding sequence 10 (CNS10) and was later shown to be enriched with the enhancer marker H3 K27 acetylation. Further studies identified a binding site for p300 as the essential enhancer element in CNS10. Moreover, p300 physically binds to CNS10 and is required for the enhancer activity of CNS10. The depletion of p300 by siRNA resulted in significantly impaired activation of Pparg2 at the early stages of 3T3-L1 adipogenesis. In summary, our study identified a novel enhancer element on the murine Pparg2 gene and suggested a novel mechanism for the regulation of Pparg2 expression by p300 in 3T3-L1 adipogenesis. 相似文献