Molecular basis for nuclear accumulation and targeting of the inhibitor of apoptosis BIRC2.

The inhibitor of apoptosis protein BIRC2 regulates fundamental cell death and survival signaling pathways. Here we show that BIRC2 accumulates in the nucleus via binding of its second and third BIR domains, BIRC2BIR2 and BIRC2BIR3, to the histone H3 tail and report the structure of the BIRC2BIR3-H3 complex. RNA-seq analysis reveals that the genes involved in interferon and defense response signaling and cell-cycle regulation are most affected by depletion of BIRC2. Overexpression of BIRC2 delays DNA damage repair and recovery of the cell-cycle progression. We describe the structural mechanism for targeting of BIRC2BIR3 by a potent but biochemically uncharacterized small molecule inhibitor LCL161 and demonstrate that LCL161 disrupts the association of endogenous BIRC2 with H3 and stimulates cell death in cancer cells. We further show that LCL161 mediates degradation of BIRC2 in human immunodeficiency virus type 1-infected human CD4+ T cells. Our findings provide mechanistic insights into the nuclear accumulation of and blocking BIRC2.

ZZEF1 is a Histone Reader and Transcriptional Coregulator of Krüppel-Like Factors.

The ZZ-type zinc finger and EF-hand domain protein 1 (ZZEF1) is a multidomain-containing protein. Mutations of ZZEF1 has been implicated in several kinds of human diseases such as diabetes and cancers. However, the function of the ZZEF protein remains largely unknown. Here we show that ZZEF1 functions as a histone H3 reader. The second ZZ domain of ZZEF1 (ZZEF1ZZ2) binds to the N-terminus of histone H3 and is capable of accommodating common epigenetic marks on the H3 tail. The N-terminal amino acids, especially Ala1, of H3 and an acidic cavity of ZZEF1ZZ2 are critical for the ZZ-H3 interaction. RNA-seq analysis in human lung cancer cell line H1299 reveals that downregulated genes upon ZZEF1 depletion are specifically enriched in genes regulated by Krüppel-like factors. Indeed, ZZEF1 physically interacts with KLF9 and KLF6, and regulates a common set of target genes of these transcription factors. Together, our findings suggest a model in which ZZEF1 binds to histone H3 tail and promotes KLF9/6-mediated gene regulation.

Reassembly of the Biosynthetic Gene Cluster Enables High Epothilone Yield in Engineered Schlegelella brevitalea.

Epothilones, as a new class of microtubule-stabilizing anticancer drugs, exhibit strong bioactivity against taxane-resistant cells and show clinical activity for the treatment of advanced breast cancer. Additionally, they also show great potential for a central nervous system injury and Alzheimer's disease. However, due to the long fermentation period of the original producer and challenges of genetic engineering of nonribosomal peptide/polyketide (NRP/PK) megasynthase genes, the application of epothilones is severely limited. Here, we addressed these problems by reassembling a novel 56-kb epothilone biosynthetic gene cluster, optimizing the promoter of each gene based on RNA-seq profiling, and completing precursor synthetic pathways in engineered Schlegella brevitalea. Furthermore, we debottlenecked the cell autolysis by optimizing culture conditions. Finally, the yield of epothilones in shake flasks was improved to 82 mg/L in six-day fermentation. Overall, we not only constructed epothilone overproducers for further drug development but also provided a rational strategy for high-level NRP/PK compound production.

Reclassification of 'Polyangium brachysporum' DSM 7029 as Schlegelella brevitalea sp. nov.

Strain DSM 7029, isolated from a soil sample in Greece, can produce antitumour glidobactins, and has been found, as a heterologous host, to produce useful nonribosomal peptide synthetase-polyketide synthase hybrid molecules known as epothilones. This strain was originally named 'Polyangium brachysporum' of the family Polyangiaceae and the order Myxococcales. However, phylogenetic analysis of the 16S rRNA gene sequence of strain DSM 7029 indicated that it was clustered with members of Schlegelella. Significant growth occurred at 25-42 °C, pH 5.0-10.0 and in the presence of 0-0.2 % (w/v) NaCl. The predominant ubiquinone was Q-8. The major fatty acids were C16 : 1ω7c/C16 : 1ω6c, C16 : 0 and C18 : 1ω7c. The G+C content of genomic DNA was 67.51 mol%. The strain was clearly distinguishable from other neighbouring Schlegelella members and genera Caldimonas and Zhizhongheella, using phylogenetic analysis, fatty acid composition data and a range of physiological and biochemical characteristics and genome analysis. Therefore, strain DSM 7029 represents a novel species of the genus Schlegelella, for which the name Schlegelella brevitalea sp. nov. is proposed.

Complete genome sequence of the glidobactin producing strain [Polyangium] brachysporum DSM 7029.

[Polyangium] brachysporum DSM7029 can produce glidobactin, which is a peptide-based proteasome inhibitor that shows great potential as an anticancer drug. To better understand the glidobactin biosynthesis mechanism and to aid further studies of this strain, we report the annotated complete genome sequence of DSM7029, which is 6,476,147 bp in length.