Epigenetics

The concept of epigenetics is based on genetics, not simply in vitro changes in methylation and acetylation caused by the environment, nor is it a simple transcription factor and miRNA regulation, it refers to non-DNA variation. And change the 'heritable' phenomenon of the phenotype. Many so-called epigenetic studies have not actually jumped out of the definition of classical genetics. (1) Epigenetics refers to changes in gene expression levels based on non-gene sequence changes, including DNA methylation, histone modification, chromosomal remodeling, and non-coding RNA regulation, mainly through transcription of genes. Or the regulation of the translation process affects its function and characteristics. The role of such markers is expected to be: 1 predicting individual differences in drug response or prognosis, screening for drugs, dosages, and modalities suitable for individual patients, and guiding treatment; 2 as a molecular target, initiating new tumor treatment by reversing the apparent modification of abnormalities way. (2) DNA methylation refers to the covalent bond of a methyl group at the 5' carbon position of the cytosine of the genomic CpG dinucleotide under the action of a DNA methyltransferase. Under normal circumstances, the CpG dinucleotide of the human genome "junk" sequence is relatively rare and always in a methylated state. In contrast, the human genome is about 100-1000 bp in size and is rich in CpG dinucleotides. The CpG island is always unmethylated and associated with 56% of the human genome coding genes. The results of human genome sequence analysis showed that there are about 28,890 CpG islands in the human genome, and most chromosomes have 5-15 CpG islands per 1 Mb. The average value is 10.5 CpG islands per Mb, and the number and gene density of CpG islands. Have a good correspondence. Due to the close relationship between DNA methylation and human development and tumor diseases, especially the transcriptional inactivation of tumor suppressor genes caused by methylation of CpG islands, DNA methylation has become an important research in epigenetics and epigenomics. content. (3) Abnormal epigenetics: Epige-netics believes that the occurrence of allergic diseases is the result of interactions between environmental factors and genes, and environmental factors can cause abnormal gene expression or dysfunction. Epigenetic, also known as epimutation. Environmental factors including infection, food, passive smoking, and allergens can regulate acetylation/deacetylation of histones by IFN-γ and IL-4 loci. Methylation/demethylation affects Th1/Th2 cell differentiation.