Hen vitellogenin genes: a study of the distribution of phosvitin phosphoprotein coding sequences using mRNA...

Pentadecamer DNA probes were synthesized, having complementary codons for selected unique pentapeptide sequences of low codon degeneracy present in hen phosvitin minor phosphoprotein, hen phosvitin major phosphoprotein, both phosvitin phosphoproteins. These probes were 5'-32P-labelled. Vitellogenin mRNA was isolated from estrogenized chick liver, fractionated by electrophoresis using formaldehyde/agarose gels and blot transferred to nitrocellulose paper. Relative yields of the two vitellogenin mRNAs differed with the extraction method used. The minor phosphoprotein DNA probe formed a hybrid with a 1.6 megadalton component. The remaining two probes hybridized to a 2.3 megadalton component, this being the expected size of a full-length message. The smallest polyadenylated fragment to which the major phosphoprotein DNA probe hybridized was 1.0 megadalton. The remaining two probes hybridized to fragments of 0.7 megadalton and possibly smaller. Phosvitin major phosphoprotein is concluded to be coded for by part of the larger vitellogenin mRNA, while the minor phosphoprotein is coded for by part of the smaller vitellogenin mRNA. Estimates of the distances of the hybridization sites from polyadenylated tails are also given.