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As a result of the synovial sarcoma associated t(X;18) translocation, the human SYT gene on chromosome 18 is fused to either the SSX1 or the SSX2 gene on the X chromosome. Although preliminary evidence indicates that the (fusion) proteins encoded by these genes may play a role in transcriptional regulation, little is known about their exact function. We set out to isolate interacting proteins through yeast two hybrid screening of a human cDNA library using SYT as a bait. Of the positive clones isolated, two were found to correspond to the acute leukemia t(10;11) associated AF10 gene, a fusion partner of MLL. Confirmation of these results was obtained via co-immunoprecipitation of endogenous and exogenous, epitope-tagged, SYT and AF10 proteins from cell line extracts and colocalization of epitope-tagged SYT and AF10 proteins in transfected cells. Subsequent sequential mutation analysis revealed a highly specific interaction of N-terminal SYT fragments with C-terminal AF10 fragments. The N-terminal interaction domain of the SYT protein was also found to be present in several SYT orthologs and homologs. The C-terminal interaction domain of AF10 is located outside known functional domains. Based on these results, a model is proposed in which the SYT and AF10 proteins act in concert as bipartite transcription factors. This model has implications for the molecular mechanisms underlying the development of both human synovial sarcomas and acute leukemias. Oncogene (2001) 20, 3281–3289. [ABSTRACT FROM AUTHOR]

We have previously isolated and characterized a mouse cDNA orthologous to the human synovial sarcoma asso- ciated SS18 (formerly named SSXT and SYT)cDNA.Here,we report the characterization of the genomic structure of the mouse Ss18 gene.Through in silico methods with sequence information contained in the public databases,we did the same for the human SS18 gene and two human SS18 homologous genes,SS18L1 and SS18L2.In addition,we identified a mouse Ss18 processed pseudogene and mapped it to chromosome 1, band A2-3.The mouse Ss18 gene,which is subject to extensive alternative splicing,is made up of 11 exons,spread out over approximately 45 kb of genomic sequence.The human SS18 gene is also composed of 11 exons with similar intron-exon boundaries,spreading out over about 70 kb of genomic se- quence.One alternatively spliced exon,which is not included in the published SS18 cDNA,corresponds to a stretch of sequence which we previously identified in the mouse Ss18 cDNA.The human SS18L1 gene,which is also made up of 11 exons with similar intron-exon boundaries,was mapped to chromosome 20 band q13.3.The smaller SS18L2 gene,which is composed of three exons with similar boundaries as the first three exons of the other three genes,was mapped to chromosome 3 band p21. Through sequence and mutation analyses this gene could be excluded as a candidate gene for 3p21-associated renal cell can- cer.In addition,we created a detailed BAC map around the human SS18 gene,placing it unequivocally between the CA- repeat marker AFMc014wf9 and the dihydrofolate reductase pseudogene DHFRP1.The next gene in this map,located distal to SS18,was found to be the TBP associated factor TAFII-105 (TAF2C2).Further analogies between the mouse Ss18 gene,the human SS18 gene and its two homologous genes were found in the putative promoter fragments.All four promoters resemble the promoters of housekeeping genes in that they are TATA-less and embedded in canonical CpG islands [ABSTRACT FROM AUTHOR]