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W Wahli

Publications and source records attributed to W Wahli.

131 records · Page 8Linked to original sources
PubMed1979

Vitellogenin in Xenopus laevis is encoded in a small family of genes.

Vitellogenin, the yolk protein precursor, is produced in X. laevis liver from a 6.3 kilobase (kb) mRNA. Sequences of this mRNA have been transcribed into cDNA and cloned in E. coli. Some properties of 21 of these cloned DNAs, ranging in size from 1 to 3.7 kb, have been reported by Wahli et al. (1978b). This paper reports restriction endonuclease mapping, cross hybridization, heteroduplex mapping in the electron microscope and heteroduplex melting experiments with these DNAs. We conclude that the cloned DNAs fall into two main groups of sequences which differ from each other in approximately 20% of their nucleotides. Each main group contains two subgroups which differ from each other by about 5% sequence divergence. By hybridizing cloned DNAs with restricted genomic DNA, we showed that sequences corresponding to all four sequence groups are present in a single animal. Furthermore, we have obtained tentative evidence for the presence of large intervening sequences in genomic vitellogenin DNA. Analysis of R loop molecules demonstrated that all four sequences are present in the vitellogenin mRNA population purified from individual animals. While some alternate explanations are not entirely excluded, we suggest that vitellogenin is encoded by a small family of related genes in Xenopus.

Animals↗
PubMed1978

Electron-microscopic demonstration of terminal and internal initiation sites for cDNA synthesis on vitellogenin mRNA.

cDNA synthesized on purified vitellogenin mRNA from Xenopus liver was hybridized to the template in formamide/urea at 22 degrees C to avoid degradation of the RNA. The hybrids formed were visualized by spreading for electron microscopy. Contour length measurements proved that most of the RNA molecules in the hybrids were still intact showing the expected molecular weight of 2.3 x 10(6). The hybridized cDNA corresponded on the average to 12% of the RNA length. In about 80% of the molecules the cDNA was located at one end. Since cDNA synthesis was primed by oligo(dT), the terminal duplex region marks the 3' end of the vitellogenin mRNA molecule. Internal duplex regions were mainly located at a specific position starting about 2800 nucleotides from the 3' end. Since the cDNA hybridizing at the internal position could specifically be synthesized on a vitellogenin RNA fragment isolated on poly(U)-Sepharose as an oligo(A)-containing RNA, we conclude that cDNA synthesis is not only initiated by the poly(A) of the 3' end, but also by a specific internal sequence.

Animals↗
PubMed1976

Size, complexity and abundance of a specific poly(A)-containing RNA of liver from male Xenopus induced to vitellogenin synthesis by estrogen.

Estrogen treatment of Xenopus males leads to the appearance of a new species of poly (A)-containing RNA in the liver, at a stage when large amounts of the estrogen-induced yolk precursor protein, vitellogenin, is produced. This estrogen-induced RNA sediments at 28 S and migrates on gels in aqueous solution with an apparent molecular weight of 2.0 X 10(6). Contour length measurements under denaturing conditions in the electron microscope reveal a molecular weight of 2.34 X 10(6) compared to the mouse 28-S rRNA. Labeling experiments show that the estrogen-induced RNA has a stability than the average liver poly(A)-containing RNA and represents 10-20% of the poly(a)-containing RNA in the cytoplasm after 24 h of labeling. Hybridization of complementary DNA, synthesized on the isolated estrogen-induced RNA, with its template suggests a complexity corresponding to a single species of poly(A)-containing RNA of such a high molecular weight. Hybridization of the complementary DNA with cytoplasmic poly (A)-containing RNA from estrogen-treated Xenopus males and control toads show that the estrogen-induced RNA constitutes 12-15% of all cytoplasmic poly(A)-containing RNA, and is at least 2000-fold less abundant in untreated males. Size, complexity and abundance of the estrogen-induced RNA are characteristics expected for a mRNA coding for vitellogenin.

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