Characterization of Cloned Complementary DNA Covering more than 6000 Nucleotides (97%) of Avian Vitellogenin mRNA

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Abstract
The messenger RNA coding for chicken vitellogenin, a precursor of the egg‐yolk proteins lipoviteiiin and phosvitin, is synthesized in the liver following estrogen injection. This mRNA is 6600 nucleotides long. We have previously reported the cloning and preliminary characterization of some cDNA fragments representing portions of the vitellogenin mRNA [Biochem. Biophys. Acta, 606, 34–46 (1980)]. In this paper we report the full characterization of a larger series of such clones, representing almost the entire length of the mRNA, by restriction endonuclease mapping, R‐loop mapping, RNA‐DNA hybridization and by translation in vitro of the RNA which hybridizes to the cloned DNA. From the results we conclude that the chicken vitellogenin mRNA, unlike that of Xenopus laevis, does not vary in sequence over most of its length, although some variations in the cDNA sequences were detected particularly in clones derived from the 3′ terminus of the RNA. All sequence variants appear to be present in RNA prepared from single animals. The possible origins of these minor species are discussed. Furthermore, we describe a cDNA clone complementary to an mRNA which is about the same size as vitellogenin mRNA and which codes for an egg yolk protein antigenically related to lipovitellin. This mRNA is synthesized constitutively.