Xenopus oocytes products

Sagata, N., Oskarsson, M., Copeland, T Brumbaugh, J and Vande Woude, G. F. (1988). Function of c-mos proto-oncogene product in meiotic maturation in Xenopus oocytes. Nature 335 519-525. 

Kaneko S, Nakamura S, Adachi K, Akaike A, Satoh M. Mobilization of intracellular Ca++ and stimulation of cAM P production by kappa opioid receptors in Xenopus oocytes. Mol Brain Res 1994 27 258-264. 

The Xenopus oocyte expression system can be used for characterization of products of specific mRNAs transcribed in vitro from cDNA isolates. Expression cloning of novel cDNAs, whose function can be assayed following expression, can also be performed using oocytes. In the latter case, as shown in Eig. 4.3, total mRNA is fractionated by size, and expression in oocytes is used to identify mRNA fractions capable of producing the protein of interest. The enriched mRNA fractions are used for cDNA preparation. The cDNA of interest is identified by its ability to select (by hybridization) its mRNA from the total mRNA pool. The selected mRNA is assayed again in oocytes, as shown in Fig. 4.3. Repeated rounds of this procedure with further enrichment of the desired cDNA from the pool leads to the isolation of the cDNA. Alternatively, in vitro transcription of the cDNA pool can also be used to generate mRNA for injection and assay. Component cDNAs of the pool that... 

Anabaseine Derivatives. The natural product anabaseine (140) (Fig. 14.13) was isolated from the marine worm Hoplonem-etines hydrobiologia (376). In vitro analysis found anabaseine to have approximately 20 times lower affinity than that of nicotine for rat brain nAChRs, with a fivefold selectivity for the 0 4182 subtype over the a, subtype (377, 378). In Xenopus oocytes, however, anabaseine had a twofold higher intrinsic potency than that of nicotine at the expressed a, nAChR subtype. 

Import of aminoacyl-tRNA into living cells is another approach toward in vivo production of nonnatural mutant proteins. Dougherty and coworkers microinjected [41] or electroporated [44] an aminoacyl-tRNA/mRNA pair into Xenopus oocyte to synthesize fluorescently labeled acetylcholine receptor. The microinjection method is applicable to any type of tRNA and amino acid, but the number of cells that can be treated at one time is very limited. 

A third type of Ca wave was demonstrated in Xenopus oocytes expressing acetylcholine receptors coupled to IP3 production (Lechleiter et al., 1991). While the majority of waves were planar or concentric, the latter patterns sometimes transformed into spiral waves. Although it is difficult to judge whether the waves are of type 1 or 2 in that study, because of the subtraction of successive images, waves of type 2 are clearly seen in experiments performed on the same cells under similar conditions (Brooker et al., 1990). Spiral waves of Ca have also been observed (Lipp Niggli, 1993) in single cardiac cells. 

Daar lO, White GA, Schuh SM, Ferris DK, Vande Woude GF. 1991. tpr-met oncogene product induces maturation-producing factor activation in Xenopus oocytes. Mol Cell Biol 11(12) 5985-5991. 

Nebreda AR, Martin-Zanca D, Kaplan DR, Parada LF, Santos E. 1991. Induction by NGF of meiotic maturation of Xenopus oocytes expressing the trk proto-oncogene product. Science 252(5005) 558-561. 

While translation of mRNA in cell-free systems is a convenient way of generating a primary protein product, expression in living cells is necessary if the full range of post-translational modifications, protein-protein interactions, and final cellular localization of the protein are to be investigated. Although cultured cells can be microinjected with mRNA, the Xenopus oocyte is the most robust and easily handled system for such studies. 

The absence of any noticeable inhibitory effect of thionein on the FFZZZA-independent transcription at the plasmid-encoded tRNA gene by RNA polymerase III and on the overall production of endogenous Xenopus oocyte mRNA by RNA-polymerase II (Fig. 4) indicates that, at the intracellular concentrations attained in these studies, thionein affected the transcription process exclusively at the level of the regulatory zinc finger protein and did not interfere with the transcriptional machineries. As both RNA polymerase II and III are also zinc metalloproteins and inhibitable by high concentrations of the chelator 1,10-phenantroline (cited in Coleman... 

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