The Human Genome Contains Hundreds of Genes Coding for Finger Proteins of the Krüppel Type

We have cloned a novel human autoimmune antigen in a patient suffering from rheumatoid arthritis with high levels of antibodies to the nucleolus organizer regions. Initially the human autoimmune serum was used to select a cDNA of 317 amino acids from a hamster expression library. Using the hamster DNA as a probe, we isolated the human homologous cDNA of 320 amino acids. Human and hamster polypeptides share a 95% amino acid homology. The deduced 36-kDa protein contains a putative amino-terminal NLS signal, nine cysteine-X-X-cysteine motifs highly conserved, and a carboxyl-terminal poly acidic region. Several homologous expressed sequence tags have been identified in data bases suggesting that orthologous proteins are present throughout evolution from worms to humans. A Drosophila expressed sequence tag was further completely sequenced for a full-length protein with 60% amino acid identity to the human homologue. Northern blot analysis revealed that this novel protein is widely distributed in human tissues with significantly higher expression levels in heart and skeletal muscle. Specific antibodies to the recombinant protein and transfection experiments demonstrated by immunofluorescence the localization of the protein predominantly but not exclusively to the nucleolus of interphase mammalian cells. In actinomycin D-treated cells the protein remains associated with the nucleolus but is not segregated, like other ribosomal factors such as upstream binding factor. In mitosis the protein was found to be associated with centromeres and concentrated at the midbody in cytokinesis. Transient distribution of this evolutionarily conserved zinc finger nucleolar autoantigen to the mitotic centromeres may provide the means for several aspects of cell cycle control and transcriptional regulation.

mentioning

confidence: 99%

Molecular Cloning of a Zinc Finger Autoantigen Transiently Associated with Interphase Nucleolus and Mitotic Centromeres and Midbodies

Bolı́var

Diaz

Iglesias

et al. 1999

“…A widespread transcriptional repressor motif is the KRAB-A domain (3)(4)(5)(6), which is found in approximately one-third of all zinc finger proteins of the Cys 2 His 2 class (7,8). Zinc finger proteins of the Cys 2 His 2 class represent one of the largest protein families known; the mammalian genome contains several hundred genes coding for such proteins (9), and the KRAB-A domain therefore represents a very important paradigm of transcriptional repression. Experiments from several laboratories have shown that the KRAB-A domain represses transcription both upstream and downstream of a target gene and is able to do so from a distance (5,10).…”

mentioning

confidence: 99%

Expression of the Transcriptional Repressor Protein Kid-1 Leads to the Disintegration of the Nucleolus

Huang

Philippin

O’Leary

et al. 1999

The rat Kid-1 gene codes for a 66-kDa protein with KRAB domains at the NH 2 terminus and two Cys 2 His 2 -zinc finger clusters of four and nine zinc fingers at the COOH terminus. It was the first KRAB-zinc finger protein for which a transcriptional repressor activity was demonstrated. Subsequently, the KRAB-A domain was identified as a widespread transcriptional repressor motif. We now present a biochemical and functional analysis of the Kid-1 protein in transfected cells. The full-length Kid-1 protein is targeted to the nucleolus and adheres tightly to as yet undefined nucleolar structures, leading eventually to the disintegration of the nucleolus. The tight adherence and nucleolar distribution can be attributed to the larger zinc finger cluster, whereas the KRAB-A domain is responsible for the nucleolar fragmentation. Upon disintegration of the nucleolus, the nucleolar transcription factor upstream binding factor disappears from the nucleolar fragments. In the absence of Kid-1, the KRIP-1 protein, which represents the natural interacting partner of zinc finger proteins with a KRAB-A domain, is homogeneously distributed in the nucleus, whereas coexpression of Kid-1 leads to a shift of KRIP-1 into the nucleolus. Nucleolar run-ons demonstrate that rDNA transcription is shut off in the nucleolar fragments. Our data demonstrate the functional diversity of the KRAB and zinc finger domains of Kid-1 and provide new functional insights into the regulation of the nucleolar structure.

“…The C 2 H 2 Zinc fingers have been shown to bind DNA in a sequence-specific manner, and the KRAB domain represses DNA transcription (15,36,37). However, only a few in vivo targets have been identified for these proteins.…”

Section: Disscussionmentioning

confidence: 99%

A Novel KRAB Domain-containing Zinc Finger Transcription Factor ZNF431 Directly Represses Patched1 Transcription

He¹,

Cai²,

Lim

et al. 2011

Krüppel-like zinc finger transcription factors compose the largest transcription factor family in the mammalian genome. However, the functions for the majority of these transcription factors as well as their in vivo downstream targets are not clear. We have functionally characterized a novel KRAB domain zinc finger transcription factor ZNF431 using both in vitro and in vivo assays. ZNF431 is a nuclear transcriptional repressor whose repressive activity depends on its association with HDAC1 and -2.