Controlling alpha-globin: a review of alpha-globin expression and its impact on beta-thalassemia.

Synthesis of alpha-globin and alpha-globin subunits of hemoglobin occurs at high levels during erythrocyte differentiation in a tightly controlled and coordinated fashion. Expression of alpha-globin is a fascinatingly complex process which has been meticulously defined in several recent studies, from chromatin modifications to Pol II recruitment. Following this, alpha-globin transcripts are processed and stabilized by a protein complex which binds the 3' untranslated region. Transcription and stabilization contribute to high level expression of alpha-globin. However, translation of alpha-globin at levels exceeding alpha-globin expression damages cellular membranes and results in beta-thalassemia. It is, therefore, crucial that alpha-globin proteins are properly folded and stabilized, processes which are dependent on the presence of haem and AHSP. The exceedingly well-characterized process of alpha-globin expression elegantly illustrates the complex interaction of factors which are required to balance necessary high expression against the negative impacts of overexpression.