Delineation of the protein domains responsible for SYT, SSX, and SYT-SSX nuclear localization

Exp Cell Res. 2000 Apr 10;256(1):192-202. doi: 10.1006/excr.2000.4813.


In the vast majority of synovial sarcomas the N-terminal part of the SYT protein is fused to the C-terminal part of an SSX protein, either SSX1 or SSX2. The wild-type proteins, as well as the resultant SYT-SSX1 and SYT-SSX2 fusion proteins, are localized in the nucleus. Recent studies in experimental systems indicated that the SYT protein may function as a transcriptional activator whereas the SSX proteins may act as transcriptional repressors. In the present work we created a series of deletion mutants and found that SYT and SSX depend on N-terminal and highly conserved C-terminal domains for nuclear localization, respectively. Our results also show that the SYT-SSX proteins colocalize with SSX2, a feature that depends on the presence of the C-terminal SSX sequences in the chimeric proteins. Absence of these sequences led to an altered subcellular localization, coinciding with that of SYT. Besides, we found that endogenously expressed SSX proteins colocalize with polycomb-group proteins and condensed chromosomes during mitosis, features that are also conferred by the C-terminus of SSX. Taken together, these results led us to conclude that the SSX moiety, especially the most C-terminal 34 amino acids, of the SYT-SSX fusion proteins is crucial for aberrant spatial targeting and transcriptional control within the nucleus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antigens, Neoplasm / chemistry
  • Antigens, Neoplasm / metabolism
  • COS Cells
  • Cell Line
  • Cell Nucleus / metabolism*
  • Cell Nucleus / ultrastructure
  • Cloning, Molecular
  • Conserved Sequence
  • HeLa Cells
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Neoplasm Proteins / chemistry*
  • Neoplasm Proteins / metabolism*
  • Proteins / chemistry*
  • Proteins / metabolism*
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Repressor Proteins / chemistry*
  • Repressor Proteins / metabolism*
  • Sequence Alignment
  • Sequence Deletion
  • Sequence Homology, Amino Acid
  • Transfection


  • Antigens, Neoplasm
  • Neoplasm Proteins
  • Proteins
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • Repressor Proteins
  • SS18 protein, human
  • synovial sarcoma X breakpoint proteins