The long term objective of this application is to gain an understanding of some of the factors which regulate the levels of different human hemoglobin in health and disease with special reference to certain hereditary diseases such as thalassemia and the hemoglobinopathies. A dysfunctional a-globin gene has been found to cause HbH disease and a thalassemia in subjects from two unrelated Black families. The gene in both families had already been cloned and sequenced. A dinucleotide deletion causes a frame-shift which generates a nonsense codon in mRNA. The gene will be studied in in vitro expression systems to determine the effect of the mutations on production of mRNA. As part of the study a series of mutant a genes bearing other nonsense codons at various sites will be evaluated in the same expression system. A retroviral vector system with several unique features has been constructed. This system will be used of transfer inserted colones globin genes into foreign cells. We plan to investigate the effect of a recently described putative erythroid enhancer element on the expression of transfered globin genes. An ATP-dependent proteolytic system in erythroid cells is under study. The protease in mouse erythroleukemia cells is to be purified and its relation to a similar enzyme in human erythroid cells will be determined. Monoclonal antibodies to the protease will be employed in purification and comparative analysis of function. The role of ATP in the system then can be clarified by access to purified enzyme.
The aim i s to ultimately establish the importance of this proteolytic system in disposing of excess and unstable globin chains in thalassemia and other hemoglobinopathies.
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