Phenylhydrazine-induced anaemia in goats and certain sheep carrying a βA-globin gene, leads to a switch from adult βA-globin mRNA to βC mRNA synthesis1. The βC globin chains are also transiently produced late in fetal life. The nucleotide sequence of selected fragments of cloned goat βC globin gene2 corresponds to the amino acid sequence determined some years ago3. A similar reactivation of globin genes has been reported for the baboon, Papio cynocephelus, where anaemic stress also leads to the production of fetal haemoglobin4. In the case of anaemic chicken, results of cDNA cloning and nucleotide sequencing experiments suggested that a novel type of α-globin gene, the ‘stress’ gene, is expressed5. The existence of such a gene was mainly supported by the fact that the cDNA nucleotide sequence did not agree with any known chicken α-globin chain amino acid sequence. In contrast, we now report results, including a reinvestigation of the αA-globin amino acid sequence, which reveal that in the anaemic chicken, the αA gene is expressed, and there is no evidence for a specific stress α-globin gene.

The contents of globin gene transcripts and other protein coding gene transcripts (preferentially expressed in liver) within nuclear RNA from chicken immature red blood cells were analyzed by the method of cDNA hybridization. A comparison of the hybridization values obtained from steady state nuclear RNA and pulse labeled newly synthesized nuclear RNA demonstrated, that (a) there is a vast excess of globin gene transcripts over other individual protein coding transcripts and (b) the ratio of globin gene transcripts to the amount of other protein gene transcripts is nearly the same within both RNA species. We conclude, that in chicken immature red blood cells the globin genes are transcribed either at a much higher rate than other protein coding genes or that most of the transcription products of other genes transcribed at higher rates must be degraded during or very shortly after transcription. Moreover, an accumulation of both types of transcripts was observed, as the contents of these RNA molecules was higher within steady state nuclear RNA than within the newly synthesized RNA.

By hybridization with [3H]labeled globin cDNA the contents of globin coding sequences in total nuclear RNA, poly(A)+nuclear RNA, poly(A)--nuclear RNA and polysomal RNA of chicken immature red blood cells was determined to be 0.86%, 20%, 0.42% and 1% respectively. As the poly(A)+-fraction comprises only about 2% of total nuclear RNA, globin coding sequences are distributed with 49% in the poly(A)+-fraction and with 51% in the poly(A)--fraction.