title: Evidence for translation of HPRT enzyme on maternal mRNA in early mouse embryos.
abstract: This paper presents evidence that maternal mRNA is responsible for the early increase in HPRT activity in preimplantation mouse embryos. Increase of HPRT activity is demonstrable from as early as 6 h postfertilization when there is barely detectable synthesis of embryonic RNA. The increase is sensitive to cycloheximide and thus requires protein synthesis, whereas it is insensitive to alpha-amanitin and therefore independent of mRNA synthesis. These results suggest that translation of HPRT occurs on pre-existing maternal mRNA. Embryo-coded HPRT activity is detectable by the 4- to 8-cell stage when the increase in HPRT activity becomes sensitive to alpha-amanitin. The transition from maternal- to embryo-coded enzyme activity is completed by the time of compaction. At this stage there is an unexplained yet reproducible loss of HPRT activity. Other maternally-inherited enzymes show a marked degradation occurring at a similar time. It is possible that the enzyme degradation observed reflects some common mechanism directing the changeover from maternally-derived to embryonically-derived enzymes.
mesh_terms: D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D001755:Blastocyst / Q000201:enzymology*; D002970:Cleavage Stage, Ovum / Q000201:enzymology; D003513:Cycloheximide / Q000494:pharmacology; D005260:Female; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D051379:Mice; D011247:Pregnancy; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000546:Amanitins; D012333:RNA, Messenger; D003513:Cycloheximide; D007770:L-Lactate Dehydrogenase; D007041:Hypoxanthine Phosphoribosyltransferase