Using an ATP:RNA adenyltransferase from Escherichia coli, a polyadenylic sequence was resynthesized onto rabbit globin mRNA from which the poly (A) segment had been previously removed. Conditions for obtaining a homogenous reconstituted globin mRNA preparation containing 30 adenylic residues per message molecule were determined. The reconstituted globin mRNA was microinjected into Xenopus laevis oocytes. Its stability was very similar to that of native mRNA.

Adenine Nucleotides↗

PubMed1975

Studies on maturation in Xenopus laevis oocytes. III. Energy production and requirements for protein synthesis.

The following results were obtained: 1) The oxygen comsumption of progesterone-stimulated X. laevis oocytes increases at the time of germinal vesicle (GV) breakdown. 2) Continous treatment with 1 mM KCN, 1 mM and 0.1 mM DNP completely inhibits GV breakdown. 3) Pretreatment experiments with KCN, DNP and cycloheximide show that binding of progesterone to the plasma membrane and the specific hormone receptor requires neither energy, nor protein synthesis. 4) 1 h pulses of DNP (1mM) or cycloheximide (50 mug/ml) were applied, at various time intervals after progesterone treatment: early pulses strongly delay, but do not prevent GV breakdown; late pulses just before GV breakdown induce a number of cytological abnormalities, which ultimately lead to cytolysis. The significance of these results is discussed and the hypothesis that synthesis of the maturation producing factor (MPF) requires both energy and protein synthesis is proposed.

Animals↗

PubMed1975

Cyclic nucleotides and amphibian development.

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Ambystoma↗

PubMed1975

Induction of maturation (meiosis) in Xenopus laevis oocytes by three organomercurials.

Three organomercurials, p-hydroxymercuribenzoate, p-hydroxymercuriphenylsulfonate, and mersalyl, induce maturation (meiosis) in a large percentage (20-100 percent) of Xenopus laevis oocytes. Maturation takes place even when the follicle cells which surround the oocytes have been withdrawn. Organomercurial- and progesterone-induced maturations have many features in common: they do not occur when the inducer is injected into the oocytes, they require the presence of Ca++ in the medium, they are inhibited by cycloheximide but not by actinomycin D. In both cases, the maturation producing factor and the pseudomaturation inducing factor are produced. Organomercurial-treated oocytes react normally to activating stimuli; their protein synthesis increases, but uptake of amino acids is strongly inhibited. Progesterone and p-hydroxymercuriphenyl-sulfonate act synergically in inducing maturation. The main difference between the two agents is that p-hydroxymercuriphenylsulfonate must act for several hours, whereas, short contact with progesterone is sufficient to induce maturation.

Animals↗

PubMed1975

Absence of polyadenylate segment in globin messenger RNA accelerates its degradation in Xenopus oocytes.

Rabbit globin poly(A)-free and native mRNA preparations were microinjected into Xenopus oocytes. The amount of globin message remaining after incubation of injected oocytes was determined by molecular hybridization with a radioactive complementary DNA probe, synthesized by copying globin mRNA with purified RNA-dependent DNA polymerase (reverse transcriptase) from avian myeloblastosis virus. The results show that 56 hr after injection about 85% of the poly(A)-free mRNA molecules are degraded, while native poly(A)-containing mRNA chains are almost completely preserved during the same period of time.

Animals↗

PubMed1975