Whitehead Institute for Biomedical Research, Cambridge, MA.
We report the cloning and characterization of a full-length cDNA encoding the human cytoskeletal isoform of alpha-actinin (alpha A), a ubiquitous actin-binding protein that shares structural homology with spectrin and dystrophin. The gene encodes 891 amino acids with 96%-98% sequence identity at the amino acid level to chicken nonskeletal muscle alpha A. Transient expression in COS cells produces a protein of approximately 104 kD that comigrates on SDS-PAGE with native alpha A. This alpha A gene is localized to chromosome 14q22-q24 by somatic cell hybrid and in situ hybridization analyses. Pulsed-field gel analysis of human genomic DNA revealed identically sized fragments when cDNA probes for alpha A and erythroid beta-spectrin were used; the latter gene has been previously localized to chromosome 14, band q22. These observations indicate that the genes for cytoskeletal alpha A and beta-spectrin are, in all likelihood, closely physically linked and that, in accordance with their similar structural features, they arose by partial duplication of an ancestral gene.