Analysis of the kinase‐related protein gene found at human chromosome 3q21 in a multi‐gene cluster: Organization, expression, alternative splicing, and polymorphic marker

Abstract

We report the amino acid sequence, genomic organization, tissue expression, and alternative splice patterns for the human kinase related protein (KRP) gene, as well as the discovery of a new CA repeat sequence polymorphic marker in an upstream intron of the myosin light chain kinase (MLCK) gene. The KRP/MLCK genetic locus is a prototype for a recently discovered paradigm in which an independently regulated gene for a non-enzymic protein is embedded within a larger gene for a signal transduction enzyme, and both classes of proteins are involved in the regulation of the same cellular structure. The MLCK/KRP gene cluster has been found only in higher vertebrates and is localized to human chromosome 3q21. The determination of the human KRP amino acid sequence through cDNA sequence analysis and its comparison to the exon/intron organization of the human KRP gene revealed an alternative splice pattern at the start of KRP exon 2, resulting in the insertion of a single glutamic acid in the middle of the protein. Examination of tissue distribution using Northern blot analysis revealed that the human expression pattern is more similar to the well-characterized chicken KRP gene expression pattern than to rodent or rabbit. Unexpected differences of the human gene from other species is the apparent expression of the human gene products in adult cardiac muscle, an observation that was pursued further by the production of a site-directed antiserum and immunohistochemistry analysis. The results reported here provide insight into the conserved and variable features of this late evolving genetic paradigm, raise new questions about the molecular aspects of cardiac muscle regulation, and provide tools needed for future clinical studies. The comparative analysis of the MLCK/KRP locus, combined with the recent discovery of a similar genomic relationship among other signal transduction proteins, suggest a diverse distribution of this theme among signal transduction systems in higher vertebrate genomes and indicate the utility of comparative genomics in revealing late evolving genetic paradigms.

Regulation of pulmonary endothelial barrier function by kinases

“…There are distinct isoforms of MLCK (36,127,210,249). The skeletal muscle MLCK is the only tissue-specific MLCK, inasmuch as it is expressed in adult skeletal muscle, but not in cardiac, smooth, or nonmuscular tissues.…”

MYLK (myosin light chain kinase)

“…Multiple MLCK isoforms are produced from the same MYLK gene by alternative splicing or alternative initiation (Lazar and Garcia, 1999;Verin et al, 1998b;Watterson et al, 1999). Six transcript variants have been identified that produce four kinase domainencoding isoforms and two isoforms of telokin.…”

“…The nmMLCK or smMLCK isoforms and telokin are ubiquitously expressed in various adult and fetal tissues and in cultured endothelium with qualitative expression appearing to be neither tissue-nor developmentspecific (Garcia et al, 1997a;Lazar and Garcia, 1999;Potier et al, 1995;Verin et al, 1998b;Watterson et al, 1999). The nmMLCK 1 and 2 isoforms are dominant isoforms in nonmuscle (endothelial) cells (Brown et al, 2010;Garcia et al, 1997a;Lazar and Garcia, 1999;Verin et al, 1998b).…”

“…All nmMLCK variants possess unique amino termini that are absent in the smooth muscle isoform, smMLCK, and two isoforms of telokin. The longer isoform of telokin, differing by one amino acid from its shorter version (with the aa 1790 deletion), is identical to the C-termini of nmMLCK and smMLCK isoforms shown (Watterson et al, 1999). Abbreviations: aa, amino acid; CaM, calmodulin; IgC2, immunoglobulin C-2 type domain; FN3, fibronectin type 3 domain.…”

Drosophila Stretchin-MLCK is a Novel Member of the Titin/Myosin Light Chain Kinase Family

“…Northern blot analyses show that this MLCK-related gene expresses multiple transcripts, whose sizes ranges from 3.2 to greater than 18 kb (Kojima et al, 1996;Tohtong et al, 1997), but the structure of the transcription unit responsible for these transcripts has not been de®ned. In comparison, the chicken and human sm/nmMLCK genes also produce multiple transcripts, ranging from 2.7 to 9 kb in size, which in turn are translated into proteins whose size ranges from 17 to 210 kDa (Collinge et al, 1992;Watterson et al, 1995Watterson et al, , 1999Birukov et al, 1998). This``embedded gene'' concept enables a single transcription unit to produce several transcripts and protein isoforms via internal promoters and alternative translation starts (Watterson et al, 1995(Watterson et al, , 1999Birukov et al, 1998;Smith et al, 1998).…”