ZNF552, a novel human KRAB/C2H2 zinc finger protein, inhibits AP-1- and SRE-mediated transcriptional activity.

In this study, we report the identification and characterization of a novel C2H2 zinc finger protein, ZNF552, from a human embryonic heart cDNA library. ZNF552 is composed of three exons and two introns and maps to chromosome 19q13.43. The cDNA of ZNF552 is 2.3 kb, encoding 407 amino acids with an amino-terminal KRAB domain and seven carboxyl-terminal C2H2 zinc finger motifs in the nucleus and cytoplasm. Northern blotting analysis indicated that a 2.3 kb transcript specific for ZNF552 was expressed in liver, lung, spleen, testis and kidney, especially with a higher level in the lung and testis in human adult tissues. Reporter gene assays showed that ZNF552 was a transcriptional repressor, and overexpression of ZNF552 in the COS-7 cells inhibited the transcriptional activities of AP-1 and SRE, which could be relieved through RNAi analysis. Deletion studies showed that the KRAB domain of ZNF552 may be involved in this inhibition.

KBTBD7, a novel human BTB-kelch protein, activates transcriptional activities of SRE and AP-1.

In this study, a novel member of BTB-kelch proteins, named KBTBD7, was cloned from a human embryonic heart cDNA library. The cDNA of KBTBD7 is 3,008 bp long and encodes a protein product of 684 amino acids (77.2 kD). This protein is highly conserved in evolution across different species. Western blot analysis indicates that a 77 kD protein specific for KBTBD7 is wildly expressed in all embryonic tissues examined. In COS-7 cells, KBTBD7 proteins are localized to the cytoplasm. KBTBD7 is a transcription activator when fused to GAL4 DNA-binding domain. Deletion analysis indicates that the BTB domain and kelch repeat motif are main regions for transcriptional activation. Overexpression of KBTBD7 in MCF-7 cells activates the transcriptional activities of activator protein-1 (AP-1) and serum response element (SRE), which can be relieved by siRNA. These results suggest that KBTBD7 proteins may act as a new transcriptional activator in mitogen-activated protein kinase (MAPK) signaling. [BMB reports 2010; 43(1): 17-22].