Furthermore, histone proteins can undergo extensive post-translational modification, including methylation, acetylation, phosphorylation, and ubiquitylation. Therefore, the position of nucleosomes at gene promoters and regulatory elements can modulate transcriptional output. For example, the intimate association between DNA and histone octamers within nucleosomes can occlude the binding of TFs and RNA Polymerase II (RNAPII) (reviewed in Li et al., Levine et al. However, in eukaryotes, the chromatin template on which transcription occurs can also profoundly affect how gene expression is established and maintained. This regulation primarily relies on site-specific DNA-binding transcription factors (TFs), which shape how the transcriptional machinery engages with gene promoters to initiate transcription. The precise control of gene transcription is required for cellular homeostasis and to establish the cell type-specific gene expression patterns that are necessary for complex multicellular development. Here we will discuss our understanding of the emerging relationship between CGIs, H3K4me3, and gene expression. Through studying H3K4me3 at CGIs it has become clear that CGIs shape the distribution of H3K4me3 and, in turn, H3K4me3 influences the chromatin landscape at CGIs. This is exemplified by the trimethylation of histone H3 at lysine 4 (H3K4me3), which is enriched at CGI-associated gene promoters and correlates with transcriptional activity. CGIs integrate the activity of a range of chromatin-regulating factors that can post-translationally modify histones and modulate gene expression. However, approximately 70% of vertebrate gene promoters are associated with DNA elements called CpG islands (CGIs) that are refractory to DNA methylation. In vertebrates, DNA is pervasively methylated at CG dinucleotides, a modification that is repressive to transcription. In addition to transcription factors, chromatin, and its chemical modification, play a central role in regulating gene expression. The precise regulation of gene transcription is required to establish and maintain cell type-specific gene expression programs during multicellular development.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |