A new human zinc finger DNA-binding protein was identified by using a yeast one-hybrid selection system. Two versions of the cDNA, encoding the same protein, were detected that differ for a 584 bp extension at the 5' region. Sequence analysis showed that the longer clone is a full length version containing part of the 5' untranslated region. The smaller version was fused in frame with the yeast GAL4 activation domain whereas the 5' region of the longer clone displayed a stop codon interrupting the fusion with the GAL4 domain. Nevertheless, this clone activated the yeast HIS3 reporter gene with the same efficiency as the smaller version. Sequence comparison of the derived protein with the database showed that it belongs to a family of zinc finger DNA-binding proteins which regulate the expression of genes involved in cell proliferation. Expression of the protein in an in vitro system, DNA-binding studies and genetic experiments identify this factor as a new zinc finger DNA-binding protein which binds GC-rich sequences and contains a domain probably functioning as a transcriptional activator. The new human protein identified in this study was therefore named GC-box-binding zinc finger protein).