%0 Journal Article
%T The lamin protein family
%A Travis A Dittmer
%A Tom Misteli
%J Genome Biology
%D 2011
%I BioMed Central
%R 10.1186/gb-2011-12-5-222
%X The lamins were first characterized biochemically as prominent 60 to 80 kDa proteins of the nuclear lamina and eventually identified as intermediate filament (IF) proteins by sequence homology [1-6]. The name intermediate filament refers to the average diameter of assembled intermediate fibers (10 to 12 nm), which is between that of actin microfilaments (7 to 10 nm) and that of microtubules (25 nm) [7]. The nuclear lamins represent one (type V) of six subtypes of the IF superfamily, defined on the basis of genomic structure and nucleotide sequence. Lamins are present only in metazoans and seem to be restricted to the animal kingdom as no obvious homologs have been identified in the fully sequenced genomes of several lower eukaryotes, including Arabidopsis thaliana, Saccharomyces cerevisiae and Schizosaccharomyces pombe.Nuclear lamins are divided into A and B types on the basis of structural and protein features and expression patterns. In general, A-type lamins resemble B-type lamins over the amino-terminal head and central rod domain, but have an expanded carboxy-terminal tail domain that contains a unique 90 amino acid segment (Figure 1). B-type lamins are usually ubiquitously expressed, whereas A-type lamins are expressed in developmentally regulated temporal patterns. The differences between A- and B-type lamins in terms of protein structure, expression, localization patterns and biochemistry have been interpreted to reflect functional diversification.Relative to the well-conserved cytoskeletal proteins tubulin and actin, IF proteins and lamins appeared more recently in evolutionary time and have undergone large divergence in sequence. Current evidence supports the hypothesis that all IF proteins arose from a common lamin-like progenitor, because all organisms known to have IF proteins also have lamins, but not all also have cytoplasmic IF proteins (the latter would be expected if lamins had evolved from a cytoplasmic IF). For example, the Drosophila genome enco
%U http://genomebiology.com/2011/12/5/222