Identification, Characterization of a Novel Zinc Finger Protein (HZF1) Gene and Its Roles in Erythroid Differentiation and Megakaryocyte Differentiation.

A significant number of transcription factors contain evolutionarily conserved zinc finger motifs. The classical C2H2 zinc finger motif, which employs two cysteine and two histidine residues to coordinate a single zinc ion, is a maim type of the zinc finger proteins. Many of the identified C2H2 type zinc protein have been demonstrated to be transcription factors that play important roles in differentiation and development of cells and tissues of higher organisms. In this study, we obtained some novel expression sequence tags (ESTs) containing C2H2 type motifs by reverse transcription-polymerase chain reaction (RT-PCR) using RNAs derived from hemin-induced K562 cells. A cDNA encoding novel zinc finger protein (designed as HZF1) was obtained by screening the human bone marrow cDNA library using one of the ESTs as the probe. The cDNA sequences (2013 nucleotides) have been submitted to the GenBank databases under accession No. AF244088.1). Three transcripts of HZF1 gene were explored by PCR amplification of cDNAs derived from hemin-induced K562 cells. The cDNA sequences (2632 nucleotides) of the longest transcript have been submitted to the GenBank databases under accession No. DQ117529). These transcripts may result from different splicing of the pre-mRNA of HZF1 but the differences between them are only involved in 5′ non-translation region of HZF1 mRNA. BLASTN analysis revealed that HZF1 gene has four exons and three introns. The putative protein consists of 670 amino acid residues including continuous 15 C2H2 and 2 C2RH zinc finger motifs. This structure characterization and the nuclear location of the protein suggest that HZF1 may function as a transcription factor. HZF1 mRNA was detected in ubiquitous tissues and various hematopoietic cell lines. Increased HZF1 mRNA expression was observed following hemin-induction or phorbol myristate acetate (PMA)-induction of K562 cells. Both of the antisence method and RNA interference assay revealed that repression of the intrinsic expression of HZF1 blocked the hemin-induced erythroid differentiation and reduced the PMA-induced megakaryocytic differentiation of K562 cells, which suggested that HZF1 play an important part in erythroid differentiation and megakaryocytic differentiation.