The Structure and Evolution of Intermediate Filament Genes
Intermediate filaments (IF) are major cytoskeletal components of most eukaryotic cells (Lazarides, 1980; Steinert et al., 1984a). They have been classified into at least five distinct subclasses, each of which contains from 1 to 30 subunits encoded by separate genes (Lazarides, 1980; Fuchs and Hanakoglu, 1983). These genes are differentially expressed in different tissues and during different stages of differentiation (Lazarides, 1980; Steinert et al., 1984a; Fuchs and Hanukoglu, 1983; Moll et al., 1982; Eichner et al., 1984; Roop et al., 1984b). We have isolated and characterized cDNA clones corresponding to the major keratins synthesized in mouse epidermis (Roop et al., 1983, 1985b). Several lines of evidence are presented which suggest that the expression of subsets of keratin genes is coordinately regulated and dependent on the state of differentiation. Analysis of amino acid sequence data deduced for these keratin subunits (Steinert et al., 1983, 1984b, 1985a) has revealed fundamental differences in the primary sequences of keratin subunits that are expressed at different states of differentiation that may alter the properties and function of filaments containing these subunits (Steinert et al., 1985a). In addition, a comparison of these amino acid sequences with those of other IF subunits (Hanakoglu and Fuchs, 1982, 1983; Quax et al., 1983; Geisler and Weber, 1982; Lewis et al., 1984) has shown that all IF subunits possess a common secondary structure, consisting of a conserved central α-helical rod domain and non-α-helical end domains of variable size and sequence.
KeywordsHeptad Repeat Intermediate Filament Keratin Gene Epidermal Keratin Primordial Gene
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