Beta-globin gene promoter generates 5′ truncated transcripts in the embryonic/fetal erythrold environment

The above paper was submitted by one of the authors (KK) without the knowledge of three of the other authors (MA, EdB and FG). We would like to add the following, after consultation with the other authors:. None of the K562 transformants with beta-globin promoter constructs shows transcription initiation from the normal cap site (+1). There are, however, transfectants that contain low amounts of a non (+1) cap initiated transcript. In the case of beta-genes, the number of transfectants is very low and although initiation at +40 is not excluded, these transcripts probably originate from the upstream vector or K562 integration site and are spliced onto position +40, as previously described for the rabbit beta-globin gene. In the case of the BH₂ transfectants, the alternative explanation is possibly more likely, i.e. the +200 transcript might originate from a cryptic promoter in the H₂K gene, rather than a spliced in transcript from an upstream promoter, because this RNA is expressed in all cases at similar levels.In either case, the normal beta-globin promoter is completely silent. We cannot conclude whether the inactivity of the promoter is caused by the presence of a trans acting suppressor factor or the absence of a trans acting factor that is required to activate the beta-globin promoter. The deleted promoter B-H2K hybrid genes were constructed to test for cis acting regulatory sequences in MEL cells, but could also be used to test for the presence of suppressor binding sequences in K562 cells. Deletion of such sequences might have led to promoter activity. However, none of the deletions up to -77bp restored activity. On this basis, it was prematurely concluded that at least part of the sequences responsiblefor the absence of normal beta-globin cap mRNA are located between -77 and +28 of the beta-globin promoter. The deletion to -77 of the beta-globin promoter renders it almost completely inactive in beta-globin expressing MEL cells (Antoniou and deBoer, unpublished) and therefore no conclusions can be drawn from the absence of detectable expression of such a promoter. However, we do know that the -208 deletion of the beta-globin gene is still active in MEL cells and that sequences upstream from -400 in the beta-globin promoter have no effect on the expression of a -400 gamma-globln promoter in K562 cells (Antoniou and deBoer, unpublished). We would therefore suggest that differences between the gamma and beta-globin genes within -208 (certainly within -400) are at least partly responsible for the lack of expression of the beta-globin gene in K562 cells.