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Spatial configuration of the chicken alpha-globin gene domain: immature and active chromatin hubs.

ABSTRACT: The spatial configuration of the chicken alpha-globin gene domain in erythroid and lymphoid cells was studied by using the Chromosome Conformation Capture (3C) approach. Real-time PCR with TaqMan probes was employed to estimate the frequencies of cross-linking of different restriction fragments within the domain. In differentiated cultured erythroblasts and in 10-day chick embryo erythrocytes expressing 'adult' alpha(A) and alpha(D) globin genes the following elements of the domain were found to form an 'active' chromatin hub: upstream Major Regulatory Element (MRE), -9 kb upstream DNase I hypersensitive site (DHS), -4 kb upstream CpG island, alpha(D) gene promoter and the downstream enhancer. The alpha(A) gene promoter was not present in the 'active' chromatin hub although the level of alpha(A) gene transcription exceeded that of the alpha(D) gene. Formation of the 'active' chromatin hub was preceded by the assembly of multiple incomplete hubs containing MRE in combination with either -9 kb DHS or other regulatory elements of the domain. These incomplete chromatin hubs were present in proliferating cultured erythroblasts which did not express globin genes. In lymphoid cells only the interaction between the alpha(D) promoter and the CpG island was detected.

SUBMITTER: Gavrilov AA

PROVIDER: S-EPMC2504291 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Spatial configuration of the chicken alpha-globin gene domain: immature and active chromatin hubs.

Gavrilov Alexey A AA Razin Sergey V SV

Nucleic acids research 20080711 14

The spatial configuration of the chicken alpha-globin gene domain in erythroid and lymphoid cells was studied by using the Chromosome Conformation Capture (3C) approach. Real-time PCR with TaqMan probes was employed to estimate the frequencies of cross-linking of different restriction fragments within the domain. In differentiated cultured erythroblasts and in 10-day chick embryo erythrocytes expressing 'adult' alpha(A) and alpha(D) globin genes the following elements of the domain were found to ...[more]

PMID: 18621783

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Project description:UNLABELLED: BACKGROUND: The ?-globin gene domains of vertebrate animals constitute popular models for studying the regulation of eukaryotic gene transcription. It has previously been shown that in the mouse the developmental switching of globin gene expression correlates with the reconfiguration of an active chromatin hub (ACH), a complex of promoters of transcribed genes with distant regulatory elements. Although it is likely that observations made in the mouse ?-globin gene domain are also relevant for this locus in other species, the validity of this supposition still lacks direct experimental evidence. Here, we have studied the spatial organization of the chicken ?-globin gene domain. This domain is of particular interest because it represents the perfect example of the so-called 'strong' tissue-specific gene domain flanked by insulators, which delimit the area of preferential sensitivity to DNase I in erythroid cells. RESULTS: Using chromosome conformation capture (3C), we have compared the spatial configuration of the ?-globin gene domain in chicken red blood cells (RBCs) expressing embryonic (3-day-old RBCs) and adult (9-day-old RBCs) ?-globin genes. In contrast to observations made in the mouse model, we found that in the chicken, the early embryonic ?-globin gene, ?, did not interact with the locus control region in RBCs of embryonic lineage (3-day RBCs), where this gene is actively transcribed. In contrast to the mouse model, a strong interaction of the promoter of another embryonic ?-globin gene, ?, with the promoter of the adult ?-globin gene, ?A, was observed in RBCs from both 3-day and 9-day chicken embryos. Finally, we have demonstrated that insulators flanking the chicken ?-globin gene domain from the upstream and from the downstream interact with each other, which places the area characterized by lineage-specific sensitivity to DNase I in a separate chromatin loop. CONCLUSIONS: Taken together, our results strongly support the ACH model but show that within a domain of tissue-specific genes, the active status of a promoter does not necessarily correlate with the recruitment of this promoter to the ACH.

Project description:BackgroundIn homeotherms, the alpha-globin gene clusters are located within permanently open genome regions enriched in housekeeping genes. Terminal erythroid differentiation results in dramatic upregulation of alpha-globin genes making their expression comparable to the rRNA transcriptional output. Little is known about the influence of the erythroid-specific alpha-globin gene transcription outburst on adjacent, widely expressed genes and large-scale chromatin organization. Here, we have analyzed the total transcription output, the overall chromatin contact profile, and CTCF binding within the 2.7 Mb segment of chicken chromosome 14 harboring the alpha-globin gene cluster in cultured lymphoid cells and cultured erythroid cells before and after induction of terminal erythroid differentiation.ResultsWe found that, similarly to mammalian genome, the chicken genomes is organized in TADs and compartments. Full activation of the alpha-globin gene transcription in differentiated erythroid cells is correlated with upregulation of several adjacent housekeeping genes and the emergence of abundant intergenic transcription. An extended chromosome region encompassing the alpha-globin cluster becomes significantly decompacted in differentiated erythroid cells, and depleted in CTCF binding and CTCF-anchored chromatin loops, while the sub-TAD harboring alpha-globin gene cluster and the upstream major regulatory element (MRE) becomes highly enriched with chromatin interactions as compared to lymphoid and proliferating erythroid cells. The alpha-globin gene domain and the neighboring loci reside within the A-like chromatin compartment in both lymphoid and erythroid cells and become further segregated from the upstream gene desert upon terminal erythroid differentiation.ConclusionsOur findings demonstrate that the effects of tissue-specific transcription activation are not restricted to the host genomic locus but affect the overall chromatin structure and transcriptional output of the encompassing topologically associating domain.

Dataset Information

Spatial configuration of the chicken alpha-globin gene domain: immature and active chromatin hubs.

Publications

Spatial configuration of the chicken alpha-globin gene domain: immature and active chromatin hubs.

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