RESUMEN
In the domain model of eukaryotic genome organization, the functional unit of the genome, along with the relevant regulatory elements, is considered to be a gene or a gene family. In hot-blooded vertebrate animals, the domains of a- and b-globin genes are positioned at different chromosomes and are organized and regulated in different fashion. In cold-blooded animals, in particular in tropical fish Danio rerio, a- and b globin genes are located in a common gene cluster. However, the joint a/b-globin gene cluster is subdivided into two development stage-specific subdomains, the adult one and the embryonic-larval one. In an attempt to find out whether this functional segregation correlates with structural segregation of the domain we compared the DNase I sensitivity and profiles of histone modifications of adult and embryonic-larval segments of the domain in cultured D. rerio fibroblasts. We have demonstrated that, in these nonerythroid cells, adult and embryonic- larval subdomains possess different DNase I sensitivities and different profiles of H3K27me3, a histone modification introduced by PRC2 complex. These observations suggest that joint a/b globin gene domain of Danio rerio is segregated into two structural subdomain harboring adult and embryonic-larval globin genes.
Asunto(s)
Cromosomas/química , Proteínas de Peces/genética , Histonas/genética , Pez Cebra/genética , Globinas alfa/genética , Globinas beta/genética , Animales , Células Cultivadas , Cromatina/química , Cromatina/metabolismo , Mapeo Cromosómico , Desoxirribonucleasa I/química , Embrión no Mamífero , Fibroblastos/citología , Fibroblastos/metabolismo , Proteínas de Peces/química , Proteínas de Peces/metabolismo , Regulación del Desarrollo de la Expresión Génica , Sitios Genéticos , N-Metiltransferasa de Histona-Lisina/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , Histonas/química , Histonas/metabolismo , Larva/citología , Larva/genética , Larva/crecimiento & desarrollo , Familia de Multigenes , Pez Cebra/crecimiento & desarrollo , Globinas alfa/química , Globinas alfa/metabolismo , Globinas beta/química , Globinas beta/metabolismoRESUMEN
The α- and ß-globin gene domains are a traditional model for study of the domain organization of the eucaryotic genome because these genes encode hemoglobin, a physiologically important protein. The α-globin and ß-globin gene domains are organized in completely different ways, while the expression of globin genes is tightly coordinated, which makes it extremely interesting to study the origin of these genes and the evolution of their regulatory systems. In this review, the organization of the α- and ß-globin gene domains and their genomic environment in different taxonomic groups are comparatively analyzed. A new hypothesis of possible evolutionary pathways for segregated α- and ß-globin gene domains of warm-blooded animals is proposed.
