The B-box zinc finger protein MdBBX20 integrates anthocyanin accumulation in response to ultraviolet radiation and low temperature.

Ultraviolet-B (UV-B) radiation and low temperature promote the accumulation of anthocyanins, which give apple skins their red colour. Although many transcription regulators have been characterized in the UV-B and low-temperature pathways, their interregulation and synergistic effects are not well understood. Here, a B-box transcription factor gene, MdBBX20, was characterized in apple and identified to promote anthocyanin biosynthesis under UV-B conditions in field experiments and when overexpressed in transgenic apple calli. The transcript level of MdBBX20 was significantly induced by UV-B. Specific G-box elements in the promoters of target genes were identified as interaction sites for MdBBX20. Further experimental interrogation of the UV-B signalling pathways showed that MdBBX20 could interact with MdHY5 in vitro and in vivo and that this interaction was required to significantly enhance the promoter activity of MdMYB1. MdBBX20 also responded to low temperature (14°C) with the participation of MdbHLH3, which directly bound a low temperature-response cis elements in the MdBBX20 promoter. These findings demonstrate the molecular mechanism by which MdBBX20 integrates low-temperature- and UV-B-induced anthocyanin accumulation in apple skin.

Comparative Study of Photoswitchable Zinc-Finger Domain and AT-Hook Motif for Light-Controlled Peptide-DNA Binding.

DNA-peptide interactions are involved in key life processes, including DNA recognition, replication, transcription, repair, organization, and modification. Development of tools that can influence DNA-peptide binding non-invasively with high spatiotemporal precision could aid in determining its role in cells and tissues. Here, the design, synthesis, and study of photocontrolled tools for sequence-specific small peptide-DNA major and minor groove interactions are reported, shedding light on DNA binding by transcriptionally active peptides. In particular, photoswitchable moieties were implemented in the peptide backbone or turn region. In each case, DNA binding was affected by photochemical isomerization, as determined in fluorescent displacement assays on model DNA strands, which provides promising tools for DNA modulation.

Light signaling differentially regulates the expression of group IV of the B-box zinc finger family.

Light is an important external signal that affects plant growth and development, such as photomorphogenesis. Transcriptional regulation defines a central regulatory mechanism in photomorphogenesis. The B-box zinc finger family consists of 32 proteins in Arabidopsis thaliana. Previous studies show that group IV of the B-box family (BBX18 to BBX25) plays either positive or negative roles in regulating photomorphogenesis. We investigated the expression patterns of BBX18 to BBX25 and the results demonstrate that the transcriptional levels of these genes are differentially regulated by the light signaling pathway.

Human in vivo dose-response to controlled, low-dose low linear energy transfer ionizing radiation exposure.

PURPOSE: The effect of low doses of low-linear energy transfer (photon) ionizing radiation (LDIR, <10 cGy) on human tissue when exposure is under normal physiologic conditions is of significant interest to the medical and scientific community in therapeutic and other contexts. Although, to date, there has been no direct assessment of the response of human tissue to LDIR when exposure is under normal physiologic conditions of intact three-dimensional architecture, vasculature, and cell-cell contacts (between epithelial cells and between epithelial and stromal cells). EXPERIMENTAL DESIGN: In this article, we present the first data on the response of human tissue exposed in vivo to LDIR with precisely controlled and calibrated doses. We evaluated transcriptomic responses to a single exposure of LDIR in the normal skin of men undergoing therapeutic radiation for prostate cancer (research protocol, Health Insurance Portability and Accountability Act-compliant, Institutional Review Board-approved). Using newly developed biostatistical tools that account for individual splice variants and the expected variability of temporal response between humans even when the outcome is measured at a single time, we show a dose-response pattern in gene expression in a number of pathways and gene groups that are biologically plausible responses to LDIR. RESULTS: Examining genes and pathways identified as radiation-responsive in cell culture models, we found seven gene groups and five pathways that were altered in men in this experiment. These included the Akt/phosphoinositide-3-kinase pathway, the growth factor pathway, the stress/apoptosis pathway, and the pathway initiated by transforming growth factor-beta signaling, whereas gene groups with altered expression included the keratins, the zinc finger proteins and signaling molecules in the mitogen-activated protein kinase gene group. We show that there is considerable individual variability in radiation response that makes the detection of effects difficult, but still feasible when analyzed according to gene group and pathway. CONCLUSIONS: These results show for the first time that low doses of radiation have an identifiable biosignature in human tissue, irradiated in vivo with normal intact three-dimensional architecture, vascular supply, and innervation. The genes and pathways show that the tissue (a) does detect the injury, (b) initiates a stress/inflammatory response, (c) undergoes DNA remodeling, as suggested by the significant increase in zinc finger protein gene expression, and (d) initiates a "pro-survival" response. The ability to detect a distinct radiation response pattern following LDIR exposure has important implications for risk assessment in both therapeutic and national defense contexts.

Molecular cloning and characterization of the human KIN17 cDNA encoding a component of the UVC response that is conserved among metazoans.

We describe the cloning and characterization of the human KIN17 cDNA encoding a 45 kDa zinc finger nuclear protein. Previous reports indicated that mouse kin17 protein may play a role in illegitimate recombination and in gene regulation. Furthermore, overproduction of mouse kin17 protein inhibits the growth of mammalian cells, particularly the proliferation of human tumour-derived cells. We show here that the KIN17 gene is remarkably conserved during evolution. Indeed, the human and mouse kin17 proteins are 92.4% identical. Furthermore, DNA sequences from fruit fly and filaria code for proteins that are 60% identical to the mammalian kin17 proteins, indicating conservation of the KIN17 gene among metazoans. The human KIN17 gene, named (HSA)KIN17, is located on human chromosome 10 at p15-p14. The (HSA)KIN17 RNA is ubiquitously expressed in all the tissues and organs examined, although muscle, heart and testis display the highest levels. UVC irradiation of quiescent human primary fibroblasts increases (HSA)KIN17 RNA with kinetics similar to those observed in mouse cells, suggesting that up-regulation of the (HSA)KIN17 gene after UVC irradiation is a conserved response in mammalian cells. (HSA)kin17 protein is concentrated in intranuclear focal structures in proliferating cells as judged by indirect immunofluorescence. UVC irradiation disassembles (HSA)kin17 foci in cycling cells, indicating a link between the intranuclear distribution of (HSA)kin17 protein and the DNA damage response.

Wig-1, a new p53-induced gene encoding a zinc finger protein.

Wild type p53 expressed from a temperature-sensitive (ts p53) construct induces both G1 cell cycle arrest and apoptosis in the p53-negative J3D mouse T lymphoma line (Wang et al., 1995). Using differential display analysis, we have identified one new p53-induced gene, wig-1 (for wild type p53-induced gene 1), whose 7.6 kb and 2.2 kb transcripts are upregulated in ts p53-transfected J3D cells following induction of wild type p53 expression by temperature shift to 32 degrees C. The wig-1 transcripts were also induced in irradiated NIH3T3 and p21-/- fibroblasts but not in irradiated p53-/- fibroblasts. Whole body gamma irradiation caused induction of both wig-1 transcripts in mouse brain, testis, kidney, spleen and lung. A basal wig-1 expression was detected in brain, testis and kidney. The WIG-1 protein contains three zinc finger motifs and a putative nuclear localization signal.