The transcription factor NF-E2, a heterodimeric protein complex composed of p45 and small Maf family proteins, is considered crucial for the regulation of erythroid gene expression and platelet formation. To facilitate the characterization of NF-E2 functions in human cells, we isolated cDNAs encoding two members of the small Maf family, MafK and MafG. The human mafK and mafG genes encode proteins of 156 and 162 amino acid residues, respectively, whose deduced amino acid sequences show approximately 95% identity to their respective chicken counterparts. Expression of mafK mRNA is high in heart, skeletal muscle and placenta, whereas mafG mRNA is abundant in skeletal muscle and is moderately expressed in heart and brain. Both are expressed in all hematopoietic cell lines, including those of erythroid and megakaryocytic lineages. In electrophoretic gel mobility shift assays binding to NF-E2 sites was found to depend on formation of homodimers or heterodimers with p45 and p45-related CNC family proteins. The results suggest that the small Maf family proteins function in human cells through interaction with various basic-leucine zipper-type transcription factors.

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Acute megakaryoblastic leukaemia (M7) and transient myeloproliferative disorder in Down's syndrome (TMD) are characterized by rapid growth of abnormal blast cells which express megakaryocytic markers. To clarify properties of the blast cells in M7 and TMD cases, we examined erythroid markers expression in blasts from six cases with M7 and seven cases with TMD in this study. Erythroid-specific mRNAs encoding gamma-globin and erythroid delta-aminolevulinate synthase were found to be expressed in blasts from most of these cases, indicating that majorities of the blasts in M7 and TMD cases have erythroid and megakaryocytic phenotypes. We also found that mRNAs encoding GATA-1 and GATA-2 are expressed in all these cases. These results suggest that M7 blasts and TMD blasts correspond to the erythroid/megakaryocytic bipotential progenitor cells.

The present investigation was conducted to determine serum levels of basic fibroblast growth factor (FGF) by enzyme immunoassay in patients with various urogenital tumors. Renal cell carcinoma had a higher tendency (28 of 52, 53.8%) toward increased serum levels of basic FGF than any of the other urogenital tumors, and increased serum basic FGF was detected more frequently in patients with advanced renal cell carcinoma. Analysis of histological pattern indicated that renal cell carcinoma with a solid or tubular component is more likely to produce basic FGF. However, no significant difference was seen between the percentage of clear cell type tumor patients with increased serum basic FGF (50.0%) and the percentage of granular cell type tumor patients with increased serum basic FGF (66.7%). Five of 8 patients with renal cell carcinoma who underwent selective renal venous sampling before nephrectomy showed increased serum basic FGF in the renal vein from the affected kidney. After resection of the affected kidney to remove the cancer, serum basic FGF disappeared within 2 weeks. However, residual huge tumor or postoperative disease prolonged the increased levels of basic FGF in 2 patients, indicating that basic FGF is produced from and secreted by tumor tissue itself. These findings suggest that serum basic FGF can be useful in the diagnosis, and in evaluating the prognosis, of patients with renal cell carcinoma.