How do cells regulate gene expression?

In eukaryotic cells, gene expression is regulated through transcriptional activators and repressors. Transcription factors are proteins that bind to specific DNA sequences near the gene promoter regions and either enhance (activators) or repress (repressors) transcription. Epigenetic modifications, such as DNA methylation and histone modifications, can influence gene expression without changing the underlying DNA sequence. For example, methyl groups added to DNA can inhibit transcription by blocking the binding of transcription factors. Histone modifications can change how tightly DNA is wound around histone proteins, influencing gene expression. Many long non-coding RNAs (lncRNAs) are found in the vicinity of chromatin, where they can interact with proteins. These interactions can either assist or hinder the ability of these proteins to bind to specific regions of DNA and carry out their functions.