Nucleic Acids Research Advance Access published online on June 30, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp545
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Gene Regulation, Chromatin, and Epigenetics |
Differential requirement of a distal regulatory region for pre-initiation complex formation at globin gene promoters
1Maisonneuve-Rosemont Hospital Research Center and Faculty of Medicine, University of Montreal, 5415 boulevard de l'Assomption, Montreal, Quebec, Canada H1T 2M4, 2Institute for Research in Immunology and Cancer (IRIC), University of Montreal, C.P. Succursale Centre-ville, Montreal, Quebec, Canada H3T 3J7 and 3Institut de recherches cliniques de Montréal (IRCM), Faculty of Medicine, University of Montreal, 110, avenue des Pins Ouest, Montreal, Quebec, Canada H2W 1R7
*To whom correspondence should be addressed. Tel: +1 514 252 3551; Fax: +1 514 252 3430; Email: e.milot.1{at}umontreal.ca
Received January 29, 2009. Revised June 9, 2009. Accepted June 10, 2009.
Although distal regulatory regions are frequent throughout the genome, the molecular mechanisms by which they act in a promoter-specific manner remain to be elucidated. The human β-globin locus constitutes an extremely well-established multigenic model to investigate this issue. In erythroid cells, the β-globin locus control region (LCR) exerts distal regulatory function by influencing local chromatin organization and inducing high-level expression of individual β-like globin genes. Moreover, in transgenic mice expressing the entire human β-globin locus, deletion of LCR-hypersensitive site 2 (HS2) can alter β-like globin gene expression. Here, we show that abnormal expression of human β-like globin genes in the absence of HS2 is associated with decreased efficacy of pre-initiation complex formation at the human 
- and 
-promoters, but not at the β-promoter. This promoter-specific phenomenon is associated with reduced long-range interactions between the HS2-deleted LCR and human -promoters. We also find that HS2 is dispensable for high-level human β-gene transcription, whereas deletion of this hypersensitive site can alter locus chromatin organization; therefore the functions exerted by HS2 in transcriptional enhancement and locus chromatin organization are distinct. Overall, our data delineate one mechanism whereby a distal regulatory region provides promoter-specific transcriptional enhancement.