Reconstitution of enhancer function in paternal pronuclei of one-cell mouse embryos.
How chromatin-mediated transcription regulates the beginning of mammalian development is currently unknown. Factors responsible for promoter repression and enhancer-mediated relief of this repression are not present in the paternal pronuclei of one-cell mouse embryos but are present in the zygotic nuclei of two-cell embryos. Here we show that coinjection of purified histones and a plasmid-encoded reporter gene into the paternal pronuclei of one-cell embryos at a specific histone-DNA concentration could recreate the behavior observed in two-cell embryos: acquisition of promoter repression and subsequent relief of this repression either by functional enhancers or by histone deacetylase inhibitors. Furthermore, the extent of enhancer-mediated stimulation in one-cell embryos depended on the acetylation status of the injected histones, on the treatment of embryos with a histone deacetylase inhibitor, and on the developmentally regulated appearance of enhancer-specific coactivator activity. The coinjected plasmids in one-cell embryos also exhibited chromatin assembly, as determined by a supercoiling assay. Thus, injection of histones into one-cell embryos faithfully reproduced the chromatin-mediated transcription observed in two-cell embryos. These results suggest that the need for enhancers to stimulate promoters through relief of chromatin-mediated repression occurs once the parental genomes are organized into chromatin. Furthermore, we present a model mammalian system in which the role of individual histones, and particular domains within the histones that are targeted in enhancer function, can be examined using purified mutant histones.
Rastelli
L
L
Department of Molecular Genetics, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030, USA.
Robinson
K
K
Xu
Y
Y
Majumder
S
S
D000818:Animals; D002843:Chromatin / Q000235:genetics*; D004247:DNA / Q000235:genetics; D004622:Embryo, Mammalian / Q000502:physiology; D005314:Embryonic and Fetal Development / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D006657:Histones / Q000235:genetics; D051379:Mice; D009154:Mutation; D014158:Transcription, Genetic
D002843:Chromatin; D006657:Histones; D004247:DNA