Characterization of transcriptionally active chicken erythrocyte chromatin

Thumbnail Image
2015-01, 2016-05, 2017-08
Jahan, Sanzida
Journal Title
Journal ISSN
Volume Title
Adv Biol Regul, Epigenetics Chromatin, J Cell Physiol.
Transcriptionally active chicken polychromatic erythrocytes are nucleated, terminally differentiated cells that are no longer replicating. Thus, provide a suitable system to study the mechanisms of transcription and transcription-related events in the absence of replication. In higher eukaryotes, genomes are organized into chromosomal domains. The combination of dynamic histone acetylation, histone modifications and histone modifying enzymes along with DNase sensitive regions ensure the conformation of the transcriptionally active chromosomal loci. Histone deacetylases (HDACs) and lysine acetyltransferases (KATs) work in combination with bromodomain-containing enzymes and chromatin remodeling factors to produce open chromatin structures. Further, protein arginine methyltransferase 1 (PRMT1), a major type I PRMT, plays a critical role in establishing and maintaining active histone marks as demonstrated for the chicken erythroid β globin domain. Type II PRMT, PRMT5 generates a modified histone, which is recognized by lysine methyltransferases complexes that contain WD repeat-containing protein 5 to establish active chromatin signature to the site. However, PRMT5-mediated arginine methylation and HDAC2 can lead to repressed chromatin state as well. Therefore, I hypothesize that the recruitment of HDAC2, PRMT1 and 5 to the active chromosomal regions is a critical event in sustaining open chromatin structure in chicken polychromatic erythrocyte cells. Several biochemical techniques along with Next-generation DNA, RNA and ChIP-sequencing, were employed in this thesis to map the salt-soluble transcriptionally active chromatin regions in chicken polychromatic erythrocyte cells (Chapter III). Our investigation revealed that chromatin structures vary with respect salt solubility and are correlated with the transcriptional status of the gene. Subsequently, we demonstrated that both total HDAC2 and HDAC2-S394ph are associated with active chromatin fractions and recruitment of HDAC2 to transcribed genes is transcriptiondependent (Chapter IV). Further, we explored the distribution of arginine modifications H3R2me2s and H4R3me2a in the active chromosomal locus (Chapter V). Genome-wide distribution of H3K4me3, H3K27ac, H3R2me2s, and H4R3me2a showed the unique distribution of these modifications with immune genes in active chromatin fractions (Chapter VI). The findings from this study will provide novel insights into the mechanisms of how HDAC2, PRMT1 and 5 regulate a complex network of gene expression. Thus, our studies supply useful information on the structural and functional organization of the chicken polychromatic erythrocyte epigenome and may also provide insights into the human erythrocyte genome organization.
Chromatin, Epigenetics, Histone acetylation, Dynamic histone acetylation