DNA encoding the heme-regulated eukaryotic initiation factor 2.alpha. kinase

Abstract

The cDNA which encodes heme-regulated eIF-2.alpha. kinase (HRI) has been cloned from a lambda Zap II cDNA library of rabbit reticulocytes. The rabbit HRI cDNA is highly homologous to human HRI and hybridizes to the human HRI DNA under moderately stringent conditions. The rabbit HRI cDNA contains 2729 amino acids. In vitro translation of HRI mRNA transcribed from HRI cDNA yields a 90 kDa polypeptide with eIF-2.alpha. kinase activity. Since HRI is a potent inhibitor of protein synthesis, it is anti-proliferative in nature. In addition, the unusually high degree of homology of HRI to three protein kinases involved in the regulation of cell division suggests that HRI plays a direct role in the regulation of cell division. Since regulation of protein synthesis is vital for cell growth and differentiation, the cDNA can be inserted into cells to manipulate proliferation and differentiation, especially of cells that are proliferating in an uncontrolled manner or characterized by arrested differentiation, such as some of the types of cancers. Initiation of protein synthesis can also be regulated by another eIF-2.alpha. kinase which is activated by double-stranded RNA (dsI) which represents an interferon-mediated response to viral infection. Deletion mutants of HRI cDNA can be constructed that are insensitive to regulation by heme, which should be more effective than native HRI in its anti-viral and anti-proliferative action.

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