Erythroid-Specific Intergenic Transcripts Originate from the 200 Kb Region 5′ to the LCR in Erythroleukemia and Human Primary Cells.

Intergenic transcripts have been discovered in globin and other multigene clusters. The role of this transcription activity in gene regulation is still unclear. We found aberrant globin gene transcripts that initiated from the regions 77 kb and 236 kb 5′ to the e gene in K562 and primary cells. The most abundant splicing form of the transcripts is a 500–600 bp RT-PCR product containing 36 bp RNA from the −240 kb region spliced to the upstream region starting at −270 bp of the e gene promoter. Several spliced transcripts also contain RNA fragments from the −77 kb region, or from the −12 kb region (between HS3 and HS2 of the LCR), or from the −8 kb region (between HS2 and HS1). A total of 17 different transcripts were found in K562 cells. Transient transfection assays showed that the −77 kb and −236 kb regions had promoter activity in K562 cells. DNase I hypersensitive sites were detected in these two regions in K562 cells, but not in Jurkat cells. The −236 promoter activity is located within the region encompassing a retrotransposon and the −77 region is located at 2 kb 5′ to an olfactory receptor gene. To test whether such aberrant transcripts occur in primary cells, we tested various human tissues. In fetal bone marrow (72 days) a spliced transcript was detected by RT-PCR and confirmed by DNA sequencing, which contained a 36 bp RNA from the −236 kb region and was spliced to the e gene promoter starting at −270 bp. Using a RNA RACE technique, we also found several aberrant globin gene transcripts in human placenta, adult bone marrow, and fetal liver (20–40 weeks, BD Biosciences). These transcripts contained 181 bp RNA from the −76 to −77 kb region 5′ and the sequence starting at −214 bp 5′ to the cap site of the e gene. While it is unclear whether these transepts or transcription itself has any biological function, this erythroid-specific transcription occurring in the 200 kb region 5′ to the LCR may play a yet-unknown role in globin gene regulation.