The zinc finger transcription factor 191 is required for early embryonic development and cell proliferation

Human zinc finger protein 191 (ZNF191/ZNF24) was cloned and characterized as a SCAN family member, which shows 94% identity to its mouse homologue zinc finger protein 191 (Zfp191). ZNF191 can specifically interact with an intronic polymorphic TCAT repeat (HUMTH01) in the tyrosine hydroxylase (TH) gene. Allelic variations of HUMTH01 have been stated to have a quantitative silencing effect on TH gene expression and to correlate with quantitative and qualitative changes in the binding by ZNF191. Zfp191 is widely expressed during embryonic development and in multiple tissues and organs in adult. To investigate the functions of Zfp191 in vivo, we have used homologous recombination to generate mice that are deficient in Zfp191. Heterozygous Zfp191(+/-) mice are normal and fertile. Homozygous Zfp191(-/-) embryos are severely retarded in development and die at approximately 7.5 days post-fertilization. Unexpectedly, in Zfp191(-/-) and Zfp191(+/-) embryos, TH gene expression is not affected. Blastocyst outgrowth experiments and the RNA interference-mediated knockdown of ZNF191 in cultured cells revealed an essential role for Zfp191 in cell proliferation. In further agreement with this function, no viable Zfp191(-/-) cell lines were obtained by derivation of embryonic stem (ES) cells from blastocysts of Zfp191(+/-) intercrosses or by forced homogenotization of heterozygous ES cells at high concentrations of G418. These data show that Zfp191 is indispensable for early embryonic development and cell proliferation.     

The maize ID1 flowering time regulator is a zinc finger protein with novel DNA binding properties

The INDETERMINATE protein, ID1, plays a key role in regulating the transition to flowering in maize. ID1 is the founding member of a plant-specific zinc finger protein family that is defined by a highly conserved amino sequence called the ID domain. The ID domain includes a cluster of three different types of zinc fingers separated from a fourth C2H2 finger by a long spacer; ID1 is distinct from other ID domain proteins by having a much longer spacer. In vitro DNA selection and amplification binding assays and DNA binding experiments showed that ID1 binds selectively to an 11 bp consensus motif via the ID domain. Unexpectedly, site-directed mutagenesis of the ID1 protein showed that zinc fingers located at each end of the ID domain are not required for binding to the consensus motif despite the fact that one of these zinc fingers is a canonical C2H2 DNA binding domain. In addition, an ID1 in vitro deletion mutant that lacks the extra spacer between zinc fingers binds the same 11 bp motif as normal ID1, suggesting that all ID domain-containing proteins recognize the same DNA target sequence. Our results demonstrate that maize ID1 and ID domain proteins have novel zinc finger configurations with unique DNA binding properties.