We report enhanced transcription from the human A gamma-globin gene promoter in nuclear extracts (NE) of erythroleukemia (K562) cells compared with that in HeLa NE. We do not observe differences in transcription levels in the two extracts with nonglobin promoter templates. Our findings, indicating preferential recognition of the globin gene promoter by nuclear factors in K562 cells, are consistent with results of studies previously reported by ourselves and others. A novel finding described here is that the addition of a double-stranded octamer motif oligonucleotide to K562 NE increases the level of transcription from the A gamma-globin gene promoter, suggesting a potential role for an octamer motif-binding factor in the repression of A gamma-globin gene transcription. A cosmid construct containing extensive human gamma- and beta-globin gene promoter and structural sequences as well as upstream control sequences also exhibits higher levels of globin gene transcription in K562 NE than in HeLa NE. Our demonstration of the feasibility of efficient, globin promoter-specific in vitro transcription of this complex template offers a novel approach for the systematic analysis of the effects of putative regulatory factors on globin gene expression in vitro in the context of a genetic environment approximating that found in vivo.

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