Development profile of polyadenylated and non-polyadenylated GAGA sub(A) receptor subunit mRNAs

The ratio of mRNA not selected for polyadenylation (non-poly(A) super(+) selected) to mRNA selected for polyadenylation (poly(A) super(+)) for the beta sub(1), alpha sub(1) and gamma sub(2) subunits of the GAGA sub(A) receptor complex was examined in rats as a function of age. Analysis of Northern blots revealed that levels of poly(A) super(+) beta sub(1) subunit mRNA were highest at 0 days of age, but decreased and reached adult levels by 5 days of postnatal age. However, levels of the beta sub(1) subunit message extracted from nonpoly(A) super(+) selected mRNA were not significantly different at any of the ages examined, suggesting the existence of a population of beta sub(1) subunit mRNA that is not polyadenylated. The age-related discrepancy between beta sub(1) subunit levels measured in non-poly(A) super(+) selected mRNA and poly(A) super(+) mRNA was also observed using solution hybridization analysis. In contrast, levels of both non-poly(A) super(+) selected mRNA and poly(A) super(+) mRNA for the alpha sub(1) subunit of the GABA sub(A) complex increased from 0 days of age to adulthood. The polyadenylated fraction of mRNA for the GABA sub(A) receptor beta sub(1), alpha sub(1) and gamma sub(2) subunit is developmentally regulated, and polyadenylated mRNA for the beta sub(1) subunit is not representative of the entire mRNA population for this subunit, as reflected by the lack of developmental change in levels of beta sub(1) subunit message extracted from non-poly(A) super(+) selected mRNA.