A transcription map for the rabbit beta-globin gene.

We have characterized the transcripts of the beta-globin gene in RNA isolated from rabbit bone marrow using the S1 mapping procedure of Berk and Sharp (1977). The largest beta-globin-specific RNA that we have detected is a transcript, colinear with the gene, that contains the mRNA coding sequences plus both intervening sequences but does not extend into the extragenic DNA sequences. The 5' and 3' ends of this pre-mRNA maps at the same position as those of mature globin mRNA. Several partially spliced RNAs are described that are probably intermediates in the pathway from the colinear transcript to mature mRNA. The largest spliced pre-mRNA has lost only about 40 of the 126 nucleotides of the small intervening sequence and contains the entire large intervening sequence together with the coding sequences. A second major intermediate pre-mRNA lacks only the entire small intervening sequence. Finally, a pre-mRNA is described in which all but approximately 90 nucleotides of the large intervening sequence have been excised. Thus both intervening sequences appear to be able to be excised in a stepwise fashion. Removal of the small intervening sequence seems to precede the removal of the large intervening sequence.