Pre-mRNA from erythroid enriched bone marrow cells of the rabbit. III. Poly(A)-, oligo(U)- and double stranded sequences.

Pre-mRNA from bone marrow of rabbits enriched in erythroid cells was analyzed by T1 and pancreatic RNase treatment and poly(U)- and poly(A)-Sepharose chromatography to contain poly(A)-, oligo(U)- and double stranded sequences. The length of the poly(A)- and oligo(U)-sequences was determined by polyacrylamide gel electrophoresis using poly(A)- and oligo(U)-standards of defined length. Poly(A) from poly(A)+pre-mRNA isolated according to the method of Holmes and Bonner shows a size distribution between 40 and 130 nucleotides with an average of 75 nucleotides. Hot phenol extraction according to Georgiev et al. leads to a smaller size of about 25 nucleotides. The oligo(U)-segment consists of 80% U and is about 25 nucleotides long. Poly(A)+ pre-mRNA of about 12000--16000 nucleotides posseses 1--2 oligo(U)-units and one double strand of about 70 nucleotide pairs. Most (greater than 90%) of the oligo(U)-and the double stranded sequences are localized at least 1700 nucleotides away from the 3'terminus. Double strands were investigated with respect to their reannealing behaviour. The material consists of two types of double strands: 20% which reassociate at a cot/2 cot/2 of 1.3 . 10(-4) represent only one or a few types of double strands, the remaining 80% reassociate at a cot/2 of about 7 . 10(-2) and are more complex. Under hybridization conditions pre-mRNA molecules are able to self-annealation. 10% of the sequences become RNase stable.