Plectin 5'-transcript diversity: short alternative sequences determine stability of gene products, initiation of translation and subcellular localization of isoforms.
Plectin is a large cytoskeletal linker protein expressed as several different isoforms from a highly complex gene. This transcript diversity is mainly caused by short 5'-sequences contained in alternative first exons. To elucidate the influence of these sequence differences and to determine potential differential functionality of the resulting protein forms, we conducted a systematic investigation of plectin isoforms on transcript and protein levels. Isoform expression was highly dependent on the different 5' ends, largely due to effects of the 5'-untranslated regions. Initiation of translation downstream of the expected start site led to loss of actin- and integrin beta4-binding in some isoforms. The small alternative N-terminal sequences (5-180 residues) profoundly affected the subcelluar localization of this >500 kDa protein. Specifically, plectin 1f was concentrated at focal adhesion contacts and plectin 1b was exclusively targeted to mitochondria, providing a connection of these organelles to intermediate filaments. Thus, with plectin as a model, we demonstrate a role for 5'-untranslated regions and alternative 5'-splicing as an important regulatory mechanism of protein expression and protein function.
Rezniczek
Günther A
GA
Institute of Biochemistry and Molecular Cell Biology, University of Vienna, Austria.
Abrahamsberg
Christina
C
Fuchs
Peter
P
Spazierer
Daniel
D
Wiche
Gerhard
G
D020121:5' Untranslated Regions / Q000235:genetics*; D017398:Alternative Splicing; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D005091:Exons; D005347:Fibroblasts / Q000166:cytology; D015870:Gene Expression; D007381:Intermediate Filament Proteins / Q000235:genetics / Q000378:metabolism*; D007614:Macropodidae; D051379:Mice / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D051190:Plectin; D014176:Protein Biosynthesis; D020033:Protein Isoforms; D014162:Transfection; D014746:Vimentin / Q000378:metabolism
D020121:5' Untranslated Regions; D002352:Carrier Proteins; D007381:Intermediate Filament Proteins; C495333:Plec protein, mouse; D051190:Plectin; D020033:Protein Isoforms; D014746:Vimentin