A carboxyl-terminal region of the ski oncoprotein mediates homodimerization as well as heterodimerization with the related protein SnoN.
Ski is a nuclear oncoprotein, and possibly a transcriptional factor, that has been shown to be involved in both transformation and myogenesis. In attempts to understand the molecular mechanisms underlying the function of Ski, the protein-protein interactions of Ski with itself and with its close relative, SnoN, were investigated. It was found that while both v-Ski and c-Ski bound themselves and each other as bacterial fusion proteins, only c-Ski formed homodimers that could be detected by covalent cross-linking of the native in vitro translated protein in solution. The results also showed that c-Ski formed heterodimers with SnoN. Deletion analysis showed that the carboxyl-terminal third of c-Ski, which is deleted in v-Ski, was required for stable dimer formation in solution. This region consists of two predicted structural motifs that constitute the c-Ski dimerization domain. The more amino-terminal motif is predicted to be mostly alpha helical and is comprised of five tandem repeats of 25 amino acids each and was required for c-Ski dimerization. The second motif is a predicted leucine zipper that was not required for dimerization but greatly increased the fraction of Ski protein detected as dimers. This minor c-Ski homodimerization domain appeared to be required for Ski-Sno heterodimer formation.
Heyman
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HC
Department of Molecular Genetics, Biochemistry, and Microbiology, College of Medicine, University of Cincinnati, Ohio 45267.
Stavnezer
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D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005091:Exons / Q000235:genetics; D016350:Leucine Zippers; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014157:Transcription Factors
D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D015682:Retroviridae Proteins, Oncogenic; D014157:Transcription Factors; C070358:v-ski protein, Avian retrovirus