Initiation of a chromatin-based transcriptionally repressive state in the preimplantation mouse embryo: lack of a primary role for expression of somatic histone H1.
A chromatin-based transcriptionally repressive state develops during the two-cell stage in preimplantation mouse embryos. Correlated with the initial formation of this state is the expression of somatic histone H1, which could confer repression by promoting the formation of a transcriptionally repressive chromatin structure. To ascertain if the expression of histone H1 could play such a primary role in initiating the formation of this transcriptionally repressive state, the endogenous pool of somatic histone H1 in the two-cell embryo was greatly expanded by injection of 25 or 100 pg of histone H1 at the one-cell stage. The expression of the transcription-requiring complex, which is an accepted marker for genome activation, was then assessed during the two-cell stage. No significant inhibition was noted following the injection of 25 pg of histone H1. A transient inhibition was observed following injection of 100 pg, but this was likely due to a delay in cleavage to the two-cell stage. We conclude that it is unlikely that the expression of somatic histone H1 is a major factor in the initial establishment of the chromatin-based transcriptionally repressive state that accompanies genome activation.
Stein
P
P
Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018, USA.
Schultz
R M
RM
D000818:Animals; D002843:Chromatin / Q000235:genetics*; D002970:Cleavage Stage, Ovum; D004261:DNA Replication / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D047108:Embryonic Development / Q000235:genetics*; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005819:Genetic Markers; D006657:Histones / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D007150:Immunohistochemistry; D051379:Mice; D018613:Microscopy, Confocal; D011247:Pregnancy; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D002843:Chromatin; D005819:Genetic Markers; D006657:Histones; D014157:Transcription Factors