A gene that encodes a protein consisting solely of zinc finger domains is preferentially expressed in transformed mouse cells.

We describe the cloning and characterization of the mouse MOK-2 gene, a new member of the Krüppel family of zinc finger proteins. Sequencing of both cDNA and genomic clones showed that the predicted MOK-2 protein consists of seven zinc finger domains with only five additional amino acids. The finger domains of MOK-2 are highly homologous to one another but not to those of other zinc finger proteins. MOK-2 is preferentially expressed in transformed cell lines, brain tissue, and testis tissue. Its possible role in cellular transformation is discussed.     

Molecular cloning and preliminary functional analysis of two novel human KRAB zinc finger proteins, HKr18 and HKr19.

cDNA clones encoding two novel human KRAB zinc finger proteins, HKr18 and HKr19, were isolated from a human testis cDNA library. Their corresponding genes were later identified in sequences originating from chromosomes 19 and 7, respectively. On the basis of the collected information from gene and cDNA sequences, Hkr18 was found to be a protein of 94 kDa with 20 zinc finger motifs in its C terminus. The HKr19 is a smaller protein, with a molecular weight of 56 kDa containing 11 zinc finger motifs. Both HKr18 and HKr19 contained a KRAB A as well as a KRAB B domain in their N termini. Northern blot analysis showed expression of HKr18 in all human tissues tested, indicating a ubiquitous expression pattern. In contrast, HKr19 showed a more restricted tissue distribution, with detectable expression primarily in testis and fetal tissues. The HKr19 protein is a member of the large ZNF91 subfamily of KRAB zinc finger genes. A PCR-based analysis of the expression of HKr19 and other closely related genes showed that lymphoid, myeloid, and nonhematopoietic cells expressed different sets of these genes. This latter finding indicates that some members of the ZNF91 family may be involved in regulating lineage commitment during hematopoietic development. Transfection of various parts of HKr19 into human embryonic kidney cells (HEK 293 cells) showed that the entire protein and its zinc finger region were toxic to these cells when expressed at high levels. In contrast, the KRAB domain and the linker region seemed to be well tolerated.     

Cloning and identification of a novel RNF6 transcriptional splice variant Spg2 in human development

RING finger proteins are zinc finger proteins containing the RING motifs. They act mainly as E3 ubiq-uitin ligases, bind the ubiquitin E2 conjugating enzyme and promote degradation of targeted proteins, Many novel genes have been isolated and differentially expressed in human adult and embryo testis by a testis cDNA-array differential display technique. A novel RING finger cDNA is highly expressed in adult testis and at low level in fetal testis. It was named Spg2. It contains a 2055 nucleotide ORF, en-codes a 685-amino-acid RNF6 protein, and has a RING finger in its C terminal. NCBI Blast shows that the gene is located on chromosome 13 and contains five exons. A multiple tissue expression profile also indicates that it is highly expressed in human testis, so we speculate that it may be associated with human spermatogenesis by virtue of the action of its RING domain.     

A factor that regulates the class II major histocompatibility complex gene DPA is a member of a subfamily of zinc finger proteins that includes a Drosophila developmental control protein.

A novel DNA sequence element termed the J element involved in the regulated expression of class II major histocompatibility complex genes was recently described. To study this element and its role in class II gene regulation further, a cDNA library was screened with oligonucleotide probes containing both the S element and the nearby J element of the human DPA gene. Several DNA clones were obtained by this procedure, one of which, clone 18, is reported and characterized here. It encodes a protein predicted to contain 688 amino acid residues, including 11 zinc finger motifs of the C2H2 type in the C-terminal region, that are Krüppel-like in the conservation of the H/C link sequence connecting them. The 160 N-terminal amino acids in the nonfinger region of clone 18 are highly homologous with similar regions of several other human, mouse, and Drosophila sequences, defining a subfamily of Krüppel-like zinc finger proteins termed TAB (tramtrack [ttk]-associated box) here. One of the Drosophila sequences, ttk, is a developmental control gene, while a second does not contain a zinc finger region but encodes a structure important in oocyte development. An acidic activation domain is located between the N-terminal conserved region of clone 18 and its zinc fingers. This protein appears to require both the S and J elements, which are separated by 10 bp for optimal binding. Antisense cDNA to clone 18 inhibited the expression of a reporter construct containing the DPA promoter, indicating its functional importance in the expression of this class II gene.     

Isolation and characterization of a novel human gene (HFB30) which encodes a protein with a RING finger motif.

A human cDNA, HFB30, encoding a novel protein that contains a RING finger (C3HC4-type zinc finger) motif was isolated. This cDNA clone consists of 3056 nucleotides and encodes an open reading frame of a 474 amino acid protein. From RT-PCR analysis, the messenger RNA was ubiquitously expressed in various human tissues. The gene was located to the chromosome 5q23.3-q31.1 region by PCR-based analyses with both a human/rodent monochromosomal hybrid cell panel and a radiation hybrid mapping panel. Furthermore, the gene consists of nine exons that span about 20 kb of genome DNA.     

Isolation of a zinc finger motif (ZNF75) mapping on chromosome Xq26.

We report here the partial characterization of a new human zinc finger (ZNF75) gene of the Kruppel type mapping to the long arm of the X chromosome. A cosmid clone was isolated from a library specific to the Xq24-qter region by hybridization to a degenerate oligonucleotide representing the link between two contigous fingers of the C2H2 type. The sequence of the pertinent cosmid fragments demonstrated five consecutive zinc finger motifs, all pertaining to the Kruppel family. A reading frame starting at least 75 amino acids before the first zinc finger and ending 11 amino acids after the last one was identified; comparison with other ZF genes suggests that this genomic fragment represents the carboxy-terminal exon of the gene. Homology of approximately 55% in the zinc finger region was detected with many zinc finger genes including mouse Zfp-35 and human ZFN7 cDNA clones. Mapping using a panel of sematic cell hybrids and chromosomal in situ hybridization localized the gene to Xq26, in a region not previously known to contain zinc finger genes.     

Cloning and characterization of a novel Krüppel-like zinc finger gene, ZNF268, expressed in early human embryo

With the aim of identifying genes involved in early human embryonic development, we have isolated a cDNA clone representing a novel human zinc finger gene ZNF268 from 3 week old human embryo cDNA library using a differential hybridization strategy. The complete cDNA sequence of ZNF268 contained an open reading frame of 2841 nucleotides that encodes a 947 amino acid protein with an N-terminal Krüppel-associated box (KRAB) domain and 24 C-terminal zinc fingers. Northern blot analysis showed that ZNF268 mRNA is mainly expressed in 3-5 week old human embryos suggesting it could play certain roles in the embryogenesis. The gene consists of six exons spanning about 22 kb of genomic DNA. According to the genomic sequence from the HTGS database, the ZNF268 gene is assigned to human chromosome 5.     

Isolation and characterization of a novel RING-H2 finger gene induced in response to cold and drought in the interfertile Citrus relative Poncirus trifoliata

Many genes in different organisms encode proteins with really interesting gene (RING) finger domain(s). The RING zinc finger domain is involved in a wide variety of functions in diverse organisms. A cDNA clone showing homology with RING zinc finger genes and nine-fold induction in response to cold was previously identified during a gene expression study in the interfertile Citrus relative Poncirus trifoliata (L.) Raf. In this study, the full-length cDNA of this clone was isolated from 2-day cold-acclimated P. trifoliata by a rapid amplification of cDNA ends method using gene-specific primers. The full-length cDNA was 956 bp containing a complete open reading frame of 474 bp encoding a polypeptide of 158 amino acids. The full-length cDNA showed a high level of homology with genes encoding putative RING zinc finger proteins in plants. The deduced amino acid sequence of this gene contained a signature sequence motif for a RING zinc finger close to the C terminus of the protein. The RING zinc finger domain was significantly similar to previously characterized RING zinc finger proteins from different organisms. Additionally, it had a histidine residue at the fifth co-ordination site, indicating that this gene encodes a RING-H2 finger protein. Northern blot hybridization showed that the expression of the RING finger gene was induced in response to cold in cold-hardy P. trifoliata but not to the same extent in cold-sensitive Citrus grandis L. Osb. (pummelo). However, the gene was induced by drought stress similarly in both the species. To our knowledge, this study presents the first isolation of the full-length sequence of a RING zinc finger gene induced in response to abiotic stress in plants and the initial characterization of this gene in Citrus .