Submitted December 17, 2007
Accepted March 27, 2008
H3K79 di-methylation marks developmental activation of the 
-globin gene but is reduced upon LCR-mediated high-level transcription
Tomoyuki Sawado, Jessica Halow, Hogune Im, Tobias Ragoczy, Emery H. Bresnick, M. A. Bender, and Mark Groudine*
Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, WA, United States
Department of Pharmacology, University of Wisconsin School of Medicine and Public Health, Madison, WI, United States
Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA, United States
* Corresponding author; email: markg{at}fhcrc.org.
Genome-wide analyses of the relationship between H3 K79 di-methylation and transcription have revealed contradictory results. To clarify this relationship at a single locus, we analyzed expression and H3 K79 modification levels at wild type and transcriptionally impaired 
-globin mutant genes during erythroid differentiation. Analysis of fractionated erythroid cells derived from WT/
LCR heterozygous mice reveals no significant H3 K79 di-methylation of the -globin gene on either allele prior to activation of transcription. Upon transcriptional activation, H3 K79 di-methylation is observed along both WT and LCR alleles, and both alleles are located in proximity to H3 K79 di-methylation nuclear foci. However, H3 K79 di-methylation is significantly increased along the LCR allele compared to the WT allele. In addition, analysis of a partial LCR deletion mutant reveals that H3 K79 di-methylation is inversely correlated with -globin gene expression levels. Thus, while our results support a link between H3 K79 di-methylation and gene expression, high levels of this mark are not essential for high level -globin gene transcription. We propose that H3 K79 di-methylation is destabilized on a highly transcribed template.
