Mark C, Looman C, Abrink M, Hellman L
Department of Cell and Molecular Biology, Biomedical Center, Uppsala, Sweden.
DNA Cell Biol. 2001 May;20(5):275-86. doi: 10.1089/104454901750232472.
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.
从人睾丸cDNA文库中分离出编码两种新型人KRAB锌指蛋白HKr18和HKr19的cDNA克隆。后来分别在源自19号和7号染色体的序列中鉴定出它们相应的基因。根据从基因和cDNA序列收集到的信息，发现Hkr18是一种94 kDa的蛋白质，其C末端有20个锌指基序。HKr19是一种较小的蛋白质，分子量为56 kDa，含有11个锌指基序。HKr18和HKr19在其N末端均含有一个KRAB A结构域以及一个KRAB B结构域。Northern印迹分析显示HKr18在所检测的所有人类组织中均有表达，表明其表达模式具有普遍性。相比之下，HKr19的组织分布更为局限，主要在睾丸和胎儿组织中检测到表达。HKr19蛋白是KRAB锌指基因的大ZNF91亚家族的成员。基于PCR对HKr19和其他密切相关基因表达的分析表明，淋巴细胞、髓细胞和非造血细胞表达这些基因的不同组合。后一发现表明ZNF91家族的一些成员可能参与造血发育过程中的谱系定向调控。将HKr19的各个部分转染到人胚肾细胞（HEK 293细胞）中表明，当高水平表达时，整个蛋白及其锌指区域对这些细胞有毒性。相比之下，KRAB结构域和连接区似乎耐受性良好。
