Human YPEL4 is a member of YPEL family. It contains a Yippee domain, which is a putative zinc-finger-like, metal-binding domain. The human YPEL4 gene maps to chromosome 11q12.1, is ubiquitously expressed in adult tissues, and encodes a nuclear protein of 127 amino acids, the function of which remains unknown. To gain insights into the cellular function of this protein, we searched for YPEL4-interacting proteins using a yeast two-hybrid screen. The major vault protein (MVP), a lung resistance associated protein, was identified as a binding partner of YPEL4. The interaction between YPEL4 and MVP in mammalian cells was further demonstrated by a series of biochemical assays including the mammalian two-hybrid assay, GST pull-down assay, co-immunoprecipitation assay, and immunocytochemistry. Using a reporter system, we found that MVP can inhibit YPEL4's ability to activate Elk-1 in the MAPK signaling pathway. This study provides new clues for understanding the molecular mechanism of YPEL4 in cell division and signal transduction pathways and should be helpful for understanding molecular functions of the YPEL family.

Background:The in vivo function of Ppm1a in mammals remains unknown. Results: Mice lacking Ppm1a developed normally but showed delayed re-epithelialization with retarded keratinocyte migration caused by overactivation of Smad2 during cutaneous wound healing. Conclusion: Ppm1a, through suppressing Smad2-mediated signaling, plays a critical role in re-epithelialization. Significance: We provided the first direct and critical genetic evidence of the in vivo role of Ppm1a.

Cardiac differentiation involves a cascade of coordinated gene expression that regulates cell proliferation and matrix protein formation in a defined temporal-spatial manner. Zinc finger-containing transcription factors have been implicated as critical regulators of multiple cardiac-expressed genes, and are thought to be important for human heart development and diseases. Here, we have identified and characterized a novel zinc finger gene named ZNF418 from a human embryo heart cDNA library. The gene spans 13.5 kb on chromosome 19q13.43 encompassing six exons, and transcribes a 3.7-kb mRNA that encodes a protein with 676 amino acid residues. The predicted protein contains a KRAB-A box and 17 tandem C2H2 type zinc finger motifs. Northern blot analysis indicates that ZNF418 is expressed in multiple fetal and adult tissues, but is expressed at higher levels in the heart. Reporter gene assays show that ZNF418 is a transcriptional repressor, and the KRAB motif of ZNF418 represents the basal repressive domain. Overexpression of ZNF418 in COS-7 cells inhibits the transcriptional activity of SRE and AP-1 which may be silenced by siRNA. These results suggest that ZNF418 is a member of the zincfinger transcription factor family and may act as a negative regulator in MAPK signaling pathway.

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Apoptosis is a widespread phenomenon and its dysregulation may result in a variety of human pathologies, such as cancer, autoimmune diseases and neurodegenerative disorders. CXXC-type zinc finger protein 5 (CXXC5) is commonly considered as a tumor suppressor undergoing deregulation or deletion in hematonosis. But it has implied involvement in apoptosis indirectly and the molecular mechanism remains unknown. In this study, we investigated CXXC5-induced apoptosis as well as its underlying mechanism. A fluorescence resonance energy transfer (FRET) assay suggested that CXXC5 induced cell death and caspase-3 activity in primary rat cortical neurons. Further colorimetric TUNEL assay, Hoechst staining and flow cytometric assay indicated a time-dependent apoptosis in which the activities of caspase-8 and caspase-3 were both regulated via CXXC5 according to enzymatic activity assay, Hoechst staining and Western blotting. Transcription reporter assay and Western blotting showed that CXXC5 resulted in activation of tumor necrosis factor-α (TNF-α), initiated the extrinsic apoptosis pathway and cross-linked with the intrinsic mitochondrial pathway. Being a bone morphogenetic protein 4 (BMP-4) downstream regulator, and also a transcription factor, cellular co-localization and co-immunoprecipitation results indicate that CXXC5 co-localized and interacted with Smads. Western blotting and nuclear fraction extraction implied that CXXC5 facilitated Smad3 phosphorylation and Smad4 nuclear translocation, and that co-expression of Smad together with CXXC5 resulted in higher TNF-α reporter activity. In sum, CXXC5 appears to regulate the TNF-α apoptosis pathway by associating with Smads.