IDENTIFICATION OF A NOVEL NUCLEAR SPECKLE-TYPE PROTEIN, SPOP

A novel antigen recognized by serum from a scleroderma patient was ide ntified by expression cloning from the HeLa cell cDNA library, The clo ned cDNA encoded a 374-amino acid protein with a relative molecular ma ss of 47 000 and a predicted amino acid sequence 62.7% identical to th e hypothetical protein of Caenorhabditis elegans, T16H12.5. The deduce d amino acid sequence had a typical POZ domain and an unidentified reg ion conserved during evolution, No zinc finger or RNA recognition moti fs were found in this clone, The 2 kbp mRNA encoding the novel clone S POP (speckle-type POZ protein) was found to be expressed in all human tissues examined, HA-tagged SPOP, transfected and overexpressed in COS 7 cells, exhibited a discrete speckled pattern in the nuclei and was c o-localized with the splicing factor, snRNP B'/B. Deletion analysis re vealed that both the POZ domain and the evolutionarily conserved regio n at the amino-terminus are required for the nuclear speckled accumula tion of SPOP. (C) 1997 Federation of European Biochemical Societies.