Identification and characterization of DSPIa, a novel isoform of human desmoplakin.
Desmoplakin is a ubiquitous component of desmosomes and desmosome-like structures, such as the cardiomyocyte area composita. Two major isoforms, desmoplakin I (DSPI) and desmoplakin II (DSPII) are encoded by alternative mRNA transcripts differentially spliced from the same gene. The resulting proteins are identical in amino acid sequence with the exception that DSPII contains only one third of the central alpha-helical rod domain present in DSPI. Here we describe a novel minor isoform of desmoplakin that is also produced by alternative splicing of the desmoplakin gene and that we name desmoplakin Ia (DSPIa). DSPIa is an alternatively spliced DSPI mRNA with a unique splice donor site that is 90% homologous to and downstream of the DSPII specific donor. The resulting DSPIa mRNA is in-frame and encodes a protein that has a central alpha-helical rod domain of intermediate size and that is 156 amino acids larger than DSPII and 443 amino acids smaller than DSPI. We demonstrate, through recombinant expression and short interfering RNA knockdown, that the DSPIa protein is readily detectable, albeit at substantially lower levels than the dominant isoforms, DSPI and DSPII. DSPIa mRNA has a similar tissue distribution to that of DSPI and of DSPII.
Centre for Cutaneous Research, Blizard Institute of Cell and Molecular Science, University of London, London, UK.
Rita M
RM
Cabral
Hong
H
Wan
Clare L
CL
Cole
Dominic J
DJ
Abrams
David P
DP
Kelsell
Andrew P
AP
South
D017398:Alternative Splicing / Q000235:genetics; D001483:Base Sequence; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000235:genetics; D051180:Desmoplakins / Q000235:genetics / Q000378:metabolism*; D000078404:Epidermal Cells; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D022821:RNA Splice Sites / Q000235:genetics; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012689:Sequence Homology, Nucleic Acid
D018076:DNA, Complementary; D051180:Desmoplakins; D020033:Protein Isoforms; D022821:RNA Splice Sites; D034741:RNA, Small Interfering