An extension of directed evolution strategies to genome-wide variations increases the chance of obtaining metabolite-overproducing microbes. However, a general high-throughput screening platform for selecting improved strains remains out of reach. Here, to expedite the evolution of metabolite-producing microbes, we utilize synthetic RNA devices comprising a riboswitch and a selection module that specifically sense inconspicuous metabolites. Using L-lysine-producing Escherichia coli as a model system, we demonstrated that this RNA device could enrich pathway-optimized strains to up to 75% of the total population after four rounds of enrichment cycles. Furthermore, the potential applicability of this device was examined by successfully extending its application to the case of L-tryptophan. When used in conjunction with combinatorial mutagenesis for metabolite overproduction, our synthetic RNA device should facilitate strain improvement.

Z-DNA, a left-handed double helical DNA is structurally different from the most abundant B-DNA. Z-DNA has been known to play a significant role in transcription and genome stability but the biological meaning and positions of Z-DNA-forming sites (ZFSs) in the human genome has not been fully explored. To obtain genome-wide map of ZFSs, Zaa with two Z-DNA-binding domains was used for ChIP-Seq analysis. A total of 391 ZFSs were found and their functions were examined in vivo. A large portion of ZFSs was enriched in the promoter regions and contain sequences with high potential to form Z-DNA. Genes containing ZFSs were occupied by RNA polymerase II at the promoters and showed high levels of expression. Moreover, ZFSs were significantly related to active histone marks such as H3K4me3 and H3K9ac. The association of Z-DNA with active transcription was confirmed by the reporter assay system. Overall, our results suggest that Z-DNA formation depends on chromatin structure as well as sequence composition, and is associated with active transcription in human cells. The global information about ZFSs positioning will provide a useful resource for further understanding of DNA structure-dependent transcriptional regulation.

ZNF224 is a Krüppel-associated box-containing zinc-finger protein which represses gene transcription by interacting with various co-repressors. However, its consensus DNA sequences and target genes are not fully identified. In this study, we identified and characterized consensus DNA sequences containing 5′-CAGC-3′; recognized by ZNF224 through ChIP-sequencing, which further confirmed by ELISA, SPR, qPCR, and luciferase activity assay. ZNF224 increased miR-663a transcription by binding to miR-663a promoter, which in turn binds to 3′; UTR of p53 and p21 to decrease their expression. miR-663a antagonist abolished ZNF224-mediated suppression of p21 and p53, resulting in the enhanced apoptosis by CPT. The analyses using human breast ductal carcinoma tissues exhibited that the expression of ZNF224 and miR-663a was increased in cancer compared to non-cancer region. Consequently, ZNF224 increases cell survival and decreases apoptosis by decreasing the expression of p53 and p21 via miR-663a as a transcriptional activator. Taken together, we identified and characterized DNA binding element of ZNF224, and its target genes, miR-663a, which provides a novel insight in the down-regulation of p21 and p53 via miR-663a by ZNF224 in breast cancer.

Objectives:The transcriptional silencing of HIV type 1 (HIV-1) provirus in latently infected cells is a major hurdle on the pathway to HIV-1 elimination. The epigenetic mechanisms established by histone modifications may affect the transcriptional silencing of HIV-1 and viral latency. A systematic epigenome profiling could be applicable to develop new epigenetic diagnostic markers for detecting HIV-1 latency.Design:The HIV-1 latency cell lines (NCHA1, NCHA2 and ACH2] were compared with CD4+ T-cell line (A3.01).Methods:The histone modification profiles obtained from chromatin immunoprecipiation followed by sequencing (ChIP-Seq) for histone H3K4me3 and H3K9ac were systematically examined and differential gene expression patterns along with levels of histone modifications were used for network analysis.Results:The HIV-1 latency gave rise to downregulation of histone H3K4me3 and H3K9ac levels in 387 and 493 regions and upregulation in 451 and 962 sites, respectively. By network analysis, five gene clusters were associated with downregulated histone modifications and six gene clusters came up with upregulated histone modifications. Integration of gene expression with epigenetic information revealed that the cell cycle regulatory genes such as CDKN1A (p21) and cyclin D2 (CCND2) identified by differentially modified histones might play an important role in maintaining the HIV-1 latency.Conclusion:The transcriptional regulation by epigenetic memory should play a key role in the evolution and maintenance of HIV-1 latency accompanied by modulation of signalling molecules in the host cells.

Although the function and the gene expression levels of histone modification enzymes showed a similar pattern in microglia and macrophages during inflammation, the expression of transcription-related elements in both cell types showed a completely different pattern.