A Proposal on Quantum Histone Modification in Gene Expression

A quantum mechanical model on histone modification is proposed. Along with the methyl / acetate or other groups bound to the modified residues the torsion angles of the nearby histone chain are supposed to participate in the quantum transition cooperatively. The transition rate W is calculated based on the non-radiative quantum transition theory in adiabatic approximation. By using W's the reaction equations can be written for histone modification and the histone modification level can be calculable from the equations, which is decided by not only the atomic group bound to the modified residue, but also the nearby histone chain. The theory can explain the mechanism for the correlation between a pair of chromatin markers observed in histone modification. The temperature dependence and the coherence-length dependence of histone modification are deduced. Several points for checking the proposed theory and the quantum nature of histone modification are suggested as follows: 1, The relationship between lnW and 1/T is same as usual protein folding. The non-Arhenius temperature dependence of the histone modification level is predicted. 2, The variation of histone modification level through point mutation of some residues on the chain is predicted since the mutation may change the coherence-length of the system. 3, Multi-site modification obeys the quantum superposition law and the comparison between multi-site transition and single modification transition gives an additional clue to the testing of the quantum nature of histone modification.Comment: 10 page

Bivalent-Like Chromatin Markers Are Predictive for Transcription Start Site Distribution in Human

Deep sequencing of 5′ capped transcripts has revealed a variety of transcription initiation patterns, from narrow, focused promoters to wide, broad promoters. Attempts have already been made to model empirically classified patterns, but virtually no quantitative models for transcription initiation have been reported. Even though both genetic and epigenetic elements have been associated with such patterns, the organization of regulatory elements is largely unknown. Here, linear regression models were derived from a pool of regulatory elements, including genomic DNA features, nucleosome organization, and histone modifications, to predict the distribution of transcription start sites (TSS). Importantly, models including both active and repressive histone modification markers, e.g. H3K4me3 and H4K20me1, were consistently found to be much more predictive than models with only single-type histone modification markers, indicating the possibility of “bivalent-like” epigenetic control of transcription initiation. The nucleosome positions are proposed to be coded in the active component of such bivalent-like histone modification markers. Finally, we demonstrated that models trained on one cell type could successfully predict TSS distribution in other cell types, suggesting that these models may have a broader application range

MicroRNA-based linkage between aging and cancer: From epigenetics view point

Ageing is a complex process and a broad spectrum of physical, psychological, and social changes over time. Accompanying diseases and disabilities, which can interfere with cancer treatment and recovery, occur in old ages. MicroRNAs (miRNAs) are a set of small non-coding RNAs, which have considerable roles in post-transcriptional regulation at gene expression level. In this review, we attempted to summarize the current knowledge of miRNAs functions in ageing, with mainly focuses on malignancies and all underlying genetic, molecular and epigenetics mechanisms. The evidences indicated the complex and dynamic nature of miRNA-based linkage of ageing and cancer at genomics and epigenomics levels which might be generally crucial for understanding the mechanisms of age-related cancer and ageing. Recently in the field of cancer and ageing, scientists claimed that uric acid can be used to regulate reactive oxygen species (ROS), leading to cancer and ageing prevention; these findings highlight the role of miRNA-based inhibition of the SLC2A9 antioxidant pathway in cancer, as a novel way to kill malignant cells, while a patient is fighting with cancer

Histone modification profiles are predictive for tissue/cell-type specific expression of both protein-coding and microRNA genes

<p>Abstract</p> <p>Background</p> <p>Gene expression is regulated at both the DNA sequence level and through modification of chromatin. However, the effect of chromatin on tissue/cell-type specific gene regulation (TCSR) is largely unknown. In this paper, we present a method to elucidate the relationship between histone modification/variation (HMV) and TCSR.</p> <p>Results</p> <p>A classifier for differentiating CD4+ T cell-specific genes from housekeeping genes using HMV data was built. We found HMV in both promoter and gene body regions to be predictive of genes which are targets of TCSR. For example, the histone modification types H3K4me3 and H3K27ac were identified as the most predictive for CpG-related promoters, whereas H3K4me3 and H3K79me3 were the most predictive for nonCpG-related promoters. However, genes targeted by TCSR can be predicted using other type of HMVs as well. Such redundancy implies that multiple type of underlying regulatory elements, such as enhancers or intragenic alternative promoters, which can regulate gene expression in a tissue/cell-type specific fashion, may be marked by the HMVs. Finally, we show that the predictive power of HMV for TCSR is not limited to protein-coding genes in CD4+ T cells, as we successfully predicted TCSR targeted genes in muscle cells, as well as microRNA genes with expression specific to CD4+ T cells, by the same classifier which was trained on HMV data of protein-coding genes in CD4+ T cells.</p> <p>Conclusion</p> <p>We have begun to understand the HMV patterns that guide gene expression in both tissue/cell-type specific and ubiquitous manner.</p

CONSERVED EXTENDED HAPLOTYPES IN MHC OF SINGAPOREAN CHINESE

Ph.DDOCTOR OF PHILOSOPH

Exploring the Epigenome of Neurons and Glia in Vitro to Determine their Utility as a Model for Alzheimer's Disease

Alzheimer’s disease is a progressive neurodegenerative condition that is characterised by distinct neuropathological changes. Within the last decade post mortem human brain samples have been used to show that there are robust epigenetic changes occurring in the brain during disease. However, as these samples are collected shortly after death they are a reflection of only the very end stages of disease. Through the exposure of differentiated adult cells to exogenous reprogramming factors it is now possible to generate induced pluripotent stem cells which have the potential to differentiate into any cell type in the body. Over recent years reseach has moved towards using these stem cells to generate neurons or microglia in order to study diseases of ageing such as Alzheimer’s disease. However, there are relatively few epigenetic studies that have been undertaken using induced pluripotent stem cells. As there are global cellular epigenetic changes occurring during the induction of pluripotency and re-differentiation it is critical to ensure we understand the DNA methylation changes occurring during normal neuronal differentiation before using these as a model of Alzheimer’s disease or other diseases of ageing. The aim of this thesis is to first characterise the DNA methylation changes that are occurring in neuronal and microglial models that are exposed to AD-relevant exposures such as differentiation and maturation, drug treatment and immune challenge. This will largely be achieved through measuring DNA methylation using the Illumina Infinium HumanMethylationEPIC BeadChip array which provides information on the DNA methylation levels at over 850,000 loci across the genome.Alzheimers Research UKAlzheimer's Societ