Human globin gene transcription in injected Xenopus oocytes: enhancement by sodium butyrate.

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Abstract
The expression of the human adult (.beta.) and fetal (.gamma.) globin genes was studied by injecting a cosmid containing the complete -G.gamma.-A.gamma.-.psi..beta.-.delta.-.beta. cluster into Xenopus oocytes. The transcripts from the .gamma. and .beta. genes were characterized with respect to their 5'' termini by S1 nuclease mapping using pores which extend 5'' to the cap site and 3'' into the 1st exon. The only .beta. transcripts detectable in injected oocytes spanned from either -231 or -177 (cap site + 1) into the 1st exon. The sensitivity of this transcription to inhibition by a low concentration of .alpha.-amanitin indicated that polymerase II was responsible. S1 analysis of .gamma. gene transcripts showed that the predominant transcript mapped from a site at -227, but a low level of transcription from the cap site was also detectable. Incubation of oocytes in saline solution containing sodium butyrate prior to injection resulted in a significant stimulation of transcription from the .gamma. gene cap site. In contrast, transcription from the .beta. gene upstream sites was only slightly increased. The possible role of sodium butyrate in promoting this effect is discussed in the context of its known property as a modifier of cellular chromatin.