Mobile genes

On page 177, Brown et al. follow the nuclear positioning of the globin genes during erythroid differentiation and find that they are often close to each other during active transcription. However, such associations do not appear to be a requirement for transcriptional regulation, but rather a consequence of it.

The α- and β-globin genes are highly transcribed for a brief time during the maturation of red blood cells, with each gene producing about the same amount of mRNA. But the chromosomal contexts for the genes are very different. The human α-globin genes lie in a gene-dense subtelomeric region that is constitutively in an open chromatin conformation. The β-globin genes are in an AT-rich region that is open only during erythroblast development.

At the point of maximal transcription, the...