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.     

A Novel Zinc Finger Gene ZNF468 with Two Co-Expressional Splice Variants, ZNF468.1 and ZNF468.2

A novel human zinc finger protein encoding gene ZNF468 was obtained from a fetal brain cDNA library. By BLAST-N analysis we found two different splice variants. We termed the two splice variants ZNF468.1 and ZNF468.2. By BLAST search against the human genome database, ZNF468 was mapped to 19q13.4. The ZNF468.1 cDNA has four exons, and the ZNF468.2 cDNA has one more, between the third and fourth exon. This extra exon creates a difference between the deduced protein N-termini of the two splice variants. The ZNF468.1 cDNA is 3906 bp in length, encoding a 522a a protein, and ZNF468.2 is 4024 bp, encoding a 469-aa-protein. Both proteins contain 11 C2H2-type zinc finger motifs at their C-termini. The N-terminus of the deduced protein of ZNF468.1 has a well-conserved Krüppel-associated box (KRAB) domain that consists of KRAB boxes A and B, whereas the protein of ZNF468.2 does not have the {KRAB} domain. Tissue distribution of the ZNF468 gene indicates that the two splice variants are widely expressed in normal human tissues, except in heart and brain, and they are also co-expressional.     

Isolation, characterization, and mapping of a novel human KRAB zinc finger protein encoding gene ZNF463

A novel human KRAB (Krüppel associated box) type zinc finger protein encoding gene, ZNF463, was obtained by mRNA differential display and RACE. It consists of 1904 nucleotides and encodes a protein of 463 amino acids with an amino-terminal KRAB domain and 12 carboxy-terminal C2H2 zinc finger units. The gene is mapped to chromosome 19q13.3 approximately 4 by FISH. As from Northern blot analysis ZNF463 is only expressed in testis, RT-PCR indicates that ZNF463 is expressed more highly in normal fertile adults than in fetus and azoospermic patients suggesting that it may play a role in human spermatogenesis.     

HUB1, a novel Krüppel type zinc finger protein, represses the human T cell leukemia virus type I long terminal repeat-mediated expression.

We have shown that human T-cell leukemia virus type I (HTLV-I) gene expression is negatively regulated by the U5 repressive element (U5RE) of its long terminal repeat (LTR). To isolate factors binding to U5RE, we screened a cDNA expression library by south-western blotting with a U5RE probe. Screening 2 x10(6) clones gave a positive clone with a 3.8 kb insert encoding a novel 671 residue polypeptide, named HTLV-I U5RE binding protein 1 (HUB1), with five zinc finger domains and a Krüppel-associated box like domain; HUB1 may be related to a repressor belonging to the Krüppel type zinc finger protein. A 4.0 kb mRNA for HUB1 is ubiquitously expressed among all human tissues tested. HUB1 recognizes the TCCACCCC sequence as a core motif and exerts a strong repressive effect on HTLV-I LTR-mediated expression. A new repressive domain, named HUB1 repressive (HUR) domain, was identified, rather than the Krüppel-associated box like domain. The N-terminal region upstream of HUR domain seemed to be also indispensable to the repression. Thus, we propose that HUB1 is a new type repressor and plays an important role in the HTLV-I U5-mediated repression.