Cancer Genetics and Epigenetics 2024, Vol.12, No.2, 106-114 http://medscipublisher.com/index.php/cge 109 covalent modifications on histones, including methylation, acetylation, and phosphorylation (Figure 2). Lysine residues on histones can be methylated, particularly on the side chains of lysine. This modification is often associated with gene silencing, as the accumulation of methylation at specific histone sites can lead to a condensed and inactive state of the gene locus. Figure 2 Factors of histone modifications Lysine residues on histones can also be acetylated, which weakens the interaction between histones and DNA by removing positive charges. This modification is usually associated with gene activation, promoting chromatin relaxation and gene transcription. Histone phosphorylation can regulate chromatin structure and affect its compactness. Phosphorylation events are often closely related to cell signaling and cell cycle regulation. Ubiquitination, the attachment of small ubiquitin proteins to histones, can also alter chromatin structure and influence gene expression. These histone modifications form a complex network within the cell nucleus, regulating gene expression and cellular function. 3.3 The role of Non-coding RNA Non-coding RNA (ncRNA) are RNA molecules that do not encode proteins but play critical roles in gene expression and cellular function. They are widely involved in the regulation of epigenetic modifications, impacting gene regulation, maintenance of chromatin structure, and various cellular biological processes. miRNAs are short non-coding RNAs, approximately 20-22 nucleotides long, that regulate gene translation and degradation by binding to the mRNA of target genes. Abnormal expression of miRNAs is closely related to the occurrence and development of various cancers, and they can act as regulators of tumor suppressor genes or oncogenes. siRNA is a type of non-coding RNA that regulates gene expression through RNA interference (RNAi). siRNA can silence target genes by specifically binding to and mediating the degradation of target mRNA. In cancer research, siRNA technology is widely used for gene silencing and the development of therapeutic strategies. lncRNAs are long non-coding RNAs that can exceed 200 nucleotides in length. lncRNAs regulate gene expression through various mechanisms, including chromatin remodeling, transcriptional regulation, and competitive binding with miRNAs. In cancer, abnormal expression of many lncRNAs is closely associated with tumor development and progression. circRNAs are closed circular RNA molecules with resistance to degradation. They can act as "sponges" for miRNAs, sequestering miRNAs and preventing them from binding to target gene mRNAs, thus influencing gene expression. These ncRNAs participate in multiple aspects of cancer, including cell cycle regulation, proliferation, and apoptosis, through complex interaction networks.
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