The structures in solution of human and rabbit beta-globin precursor messenger RNAs containing their first intervening sequence have been investigated. This was accomplished by chemical probing experiments to determine sites of potential base pairing, and by cross-linking experiments to determine the sites of long-range interactions. Secondary structures for both molecules were predicted by using this information. Both molecules are arranged into two separate domains. The first domain, consisting of the first exon, contains several long-range interactions between the beginning of the molecule and sites adjacent to the donor splice site and a partially conserved stem/loop structure. The second domain contains part of the intervening sequence and the beginning of the second exon. The secondary structures involved in the second domain are different in the two molecules. These studies indicate a lack of connection between the donor and acceptor splice sites in these two molecules on the level of the secondary structure. Furthermore, given the absence of strongly conserved structures, it is unlikely that there could be any strict requirements for secondary structures that influence splice site usage.
Animals Base Sequence