Induction of early transcription in one-cell mouse embryos by microinjection of the nonhistone chromosomal protein HMG-I.
In the mouse embryo, the onset of zygotic transcription occurs at the end of the first cell cycle, upon completion of DNA replication. We show that the nonhistone chromosomal protein HMG-I, whose translocation into the pronuclei of one-cell embryos is linked to this first round of DNA synthesis, plays a critical role in the activation of zygotic transcription. Indeed, microinjection of purified HMG-I results in a higher nuclear accumulation of the protein and triggers an earlier activation of zygotic transcription, an effect which is abolished by the preincubation of the protein with a specific antibody directed against its AT-hook DNA-binding motifs. Significantly, microinjection of this antibody also prevents the normal onset of transcription in the embryo, suggesting that endogenous HMG-I is similarly involved in this process. Finally, microinjection of the exogenous protein modifies chromatin structure as measured by in situ accessibility to DNase I. We propose that general chromosomal architectural factors such as HMG-I can modulate the accessibility of chromatin to specialized regulatory factors, thereby promoting a transcriptionally competent state.
Beaujean
N
N
Institut de Biologie Physico-Chimique, INRA 806/EA 2703, IFR 63, Muséum National d'Histoire Naturelle, 13 Rue Pierre et Marie Curie, Paris, 75005, France.
Bouniol-Baly
C
C
Monod
C
C
Kissa
K
K
Jullien
D
D
Aulner
N
N
Amirand
C
C
Debey
P
P
Käs
E
E
D000818:Animals; D002467:Cell Nucleus / Q000187:drug effects / Q000502:physiology; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D002843:Chromatin / Q000187:drug effects / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D005260:Female; D025741:HMGA1a Protein; D006609:High Mobility Group Proteins / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008845:Microinjections; D008856:Microscopy, Fluorescence; D009865:Oocytes / Q000502:physiology; D010053:Ovary; D014157:Transcription Factors / Q000008:administration & dosage / Q000494:pharmacology / Q000502:physiology*; D014158:Transcription, Genetic; D015053:Zygote / Q000166:cytology / Q000502:physiology*
D006063:Chorionic Gonadotropin; D002843:Chromatin; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D014157:Transcription Factors; D025741:HMGA1a Protein