Complexity of Poly(A)-Containing Heterogeneous Nuclear Ribonucleic Acid from Mouse Embryoid Bodies (OTT6050)

Poly(A+)-hnRNA was isolated from mouse embryoid bodies (OTT6050). We have investigated this RNA with respect to sequence complexity by using a tritiated cDNA probe to poly(A+)-hnRNA ([3H]cDNAhn). A comparison was also made with total poly(A+)-RNA from mouse embryoid bodies. Two classes of sequences were found in poly(A+)-hnRNA. They represented 50 and 46% of the sequences in the poly(A+)-hnRNA, which corresponds to 570 and 12 500 different hnRNA sequences, respectively, of an average length of 2700 nucleotides (NT) present on an average of 12 and 1 copies per cell, respectively. The total complexity in poly(A+)-hnRNA was 3.4,x 107 NT. Three classes of sequences could be detected in total poly(A+)-RNA (mainly cytoplasmic), representing 9, 61, and 25%, respectively, of the sequences in its [3H]cDNA probe. This corresponds to 12000, 620, and 16 copies per cell of poly(A+)-RNA with each class having 2, 140, and 2500 different sequences, respectively, of an average length of 1350 NT. The total complexity of the poly(A+)-RNA was 3.4 x 106 NT. This indicates that the poly(A+)-hnRNA is approximately 10 times more complex with respect to sequence information than the total poly-(A+)-RNA. The vast majority of the total poly(A+)-RNA sequences are present in the poly(A4-)-hnRNA but in much lower concentration. Total poly(A+)-RNA saturated 65% of the nuclear [3H]cDNAhn probe. This suggests that there are poly(A+)-hnRNA sequences present in the nucleus which have no major detectable counterpart in the total poly(A+)-RNA [90-96% poly(A+)-containing cytoplasmic RNA], Total poly(A+)-RNA from the more differentiated mouse neuroepithelial teratocarcinomas saturated only 37% of the nuclear [3H]cDNAhn probe from mouse embryoid bodies compared to 65% for the total poly(A+)-RNA from embryoid bodies.