Differential polyadenylation pattern of ovalbumin precursor RNAs during development

The expression of the ovalbumin gene encoding for the major hen oviduct protein slows down with age. Analysis of Northern blots of electrophoretically separated total and poly(A)+ RNA from oviducts of hens of different age with an ovalbumin-specific probe (nick-translated 9.5 kb ovalbumin gene DNA cloned into pBR322) revealed that the largest high molecular weight ovalbumin RNA precursor (7.9 kb band, representing the putative primary transcript of the ovalbumin gene) was most intense if total RNA from non-egg-laying old hen oviduct was checked as compared to that from egg-laying mature animals. On the other side, the 7.9 kb RNA precursor band was readily detected in the poly(A)+ RNA from mature hen oviduct where-as it was invisible in the old hen oviduct poly(A)+ RNA fraction. The lack of detection of the 7.9 kb RNA species within the poly(A)+ RNA fraction and its increased concentation within the total oviduct RNA, both from old animals, suggest that age-dependent impairment of ovalbumin mRNA processing may be caused by altered polyadenylation of distinct RNA precursors.