Cloning, genomic organization, and tissue distribution of human Ssf-1

During the screening of a human placenta cDNA library, realized in order to isolate the P2Y(11) coding sequence, an unrelated cDNA was cloned. We identified a 1422 bp open reading frame encoding a human protein displaying 40% amino acid identity with the Saccharomyces cerevisiae Ssf-1, a protein involved in the second step of mRNA splicing. Sequencing of the corresponding genomic DNA showed that the gene encoding human Ssf-1 is located upstream to the P2Y(11) gene on chromosome 19p31. Comparison of the cDNA and genomic DNA sequences revealed that the human Ssf-1 gene is split into 12 exons. Northern blotting experiments showed that the 1.7 kb Ssf-1 mRNA presents an ubiquitous tissue expression. We also show that, in HL-60 human promyelocytic leukemia cells, Ssf-1 mRNA is rapidly upregulated following a treatment by granulocyte-colony stimulating factor and dibutyryl-cyclicAMP, two agents known to induce the granulocytic differentiation of these cells.