Transcription of the αA‐globin gene of the duck

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Abstract
A homologous in vitro transcription system was developed in which the αA‐globin gene of the duck was faithfully transcribed. Whole‐cell extracts from duck erythrocytes were separated into fractions A, B, C and D by consecutive elution from phosphocellulose columns and were individually reconstituted in run‐off transcription assays. Fractions A, C and D were required to achieve faithful initiation on the αA‐globin gene. The latter fractions were mutually interchangeable with comparable fractions from HeLa cells. A fourth fraction, B, was not required but enhanced‐basal transcription when reconstituted with fractions A, C and D or a very low amount of HeLa whole‐cell extract which by itself did not yield a detectable signal. Fraction B from duck erythrocytes was further purified by chromatography on DEAE‐Sephadex and was shown to contain two trans‐acting factors. One of these differentially acts on the αA‐globin gene of the duck. The other component from duck erythrocytes surprisingly resembles the upstream stimulatory factor, previously isolated from HeLa cells. This latter protein binds to and trans‐activates the adenovirus 2 major late promoter, but is not involved in the transcription of the αA‐globin gene.