GATA-1 Modulates the Chromatin Structure and Activity of the Chicken α-Globin 3′ Enhancer

Abstract

Long-distance regulatory elements and local chromatin structure are critical for proper regulation of gene expression. Here we characterize the chromatin conformation of the chicken α-globin silencer-enhancer elements located 3′ of the domain. We found a characteristic and erythrocyte-specific structure between the previously defined silencer and the enhancer, defined by two nuclease hypersensitive sites, which appear when the enhancer is active during erythroid differentiation. Fine mapping of these sites demonstrates the absence of a positioned nucleosome and the association of GATA-1. Functional analyses of episomal vectors, as well as stably integrated constructs, revealed that GATA-1 plays a major role in defining both the chromatin structure and the enhancer activity. We detected a progressive enrichment of histone acetylation on critical enhancer nuclear factor binding sites, in correlation with the formation of an apparent nucleosome-free region. On the basis of these results, we propose that the local chromatin structure of the chicken α-globin enhancer plays a central role in its capacity to differentially regulate α-globin gene expression during erythroid differentiation and development.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/ .

ACKNOWLEDGMENTS

We thank Ann Dean, Gary Felsenfeld, David J. Clark, Rodolfo Ghirlando, Mayra Furlan-Magaril, Ernesto Soto-Reyes, and Paul Delgado-Olguín for helpful comments on the manuscript. We thank Georgina Guerrero for her excellent technical assistance and members of the Félix Recillas-Targa laboratory for stimulating scientific discussions and suggestions. We also thank the technical assistance of Héctor Rincón-Arano, Cristina Aranda, Estela García Conzález, and Itzel Escobedo Ávila. We thank L. Ongay, G. Codiz, and M. Mora from the Unidad de Biología Molecular from the Instituto de Fisiología Celular, UNAM, for DNA sequencing and fluorescence-activated cell sorting facility.

This work was supported by grants from the Dirección General de Asuntos del Personal Académico-UNAM (IN203200, IX230104, IN209403, and IN214407), Consejo Nacional de Ciencia y Tecnología, CONACyT (33863-N, 42653-Q, and 58767), and the Third World Academy of Sciences (TWAS, grant 01-055 RG/BIO/LA). M.E.-D.-A was a fellowship recipient from CONACyT.