title: C-myc expression is dissociated from DNA synthesis and cell division in Xenopus oocyte and early embryonic development.
abstract: The combined use of a human c-myc probe and of an antibody raised against the human c-myc gene product demonstrated that the Xenopus cells contained a 2.5-kb c-myc transcript and synthesized a c-myc immunoreactive 65-kd polypeptide. In full-grown oocytes, p65c-myc was predominantly located in the nucleus. In non-dividing Xenopus oocytes c-myc mRNA was present at a steady-state level 10(4) times higher than that of growing somatic A6 cells. This very high level of c-myc transcript was reached early in oogenesis and remained constant thereafter. The rate of p65c-myc synthesis also reached high levels, but only in vitellogenic oocytes, suggesting a post-transcriptional control. Although the cell cycle is resumed at a very fast pace in developing embryos, no further increase in total embryonic content of c-myc RNA could be demonstrated up to the swimming tadpole stage. Furthermore, in embryos the rate of synthesis of p65c-myc decreased to a level markedly lower than that of cell cycle-arrested vitellogenic oocytes. This observation suggests that the function of the c-myc gene in the cell cycle may not be implicated directly in sustaining DNA synthesis or mitosis.
mesh_terms: D000818:Animals; D002455:Cell Division; D004261:DNA Replication; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000502:physiology*; D005314:Embryonic and Fetal Development; D005260:Female; D005796:Genes; D006801:Humans; D008297:Male; D009857:Oncogenes; D009865:Oocytes / Q000166:cytology*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016271:Proto-Oncogene Proteins c-myc; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014981:Xenopus / Q000235:genetics*
chemical_list: D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc