ComF is a key mediator in single-stranded DNA transport and handling during natural transformation

Natural transformation plays a major role in the spreading of antibiotic resistances and virulence factors. Whilst bacterial species display specificities in the molecular machineries allowing transforming DNA capture and integration into their genome, the ComF(C) protein is essential for natural transformation in all Gram- positive and - negative species studied. Despite this, its role remains largely unknown. Here, we show that Helicobacter pylori ComF is not only involved in DNA transport through the cell membrane, but it also required for the handling of the ssDNA once it is delivered into the cytoplasm. ComF crystal structure revealed the presence of a zinc-finger motif and a putative phosphoribosyl transferase domain, both necessary for its in vivo activity. ComF is a membrane-associated protein with affinity for single-stranded DNA. Collectively, our results suggest that ComF provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery.

Cystathione β-synthase regulates HIF-1α stability through persulfidation of PHD2

The stringent expression of the hypoxia inducible factor-1α (HIF-1α) is critical to a variety of pathophysiological conditions. We reveal that, in normoxia, enzymatic action of cystathionine β-synthase (CBS) produces H2S, which persulfidates prolyl hydroxylase 2 (PHD2) at residues Cys21 and Cys33 (zinc finger motif), augmenting prolyl hydroxylase activity. Depleting endogenous H2S either by hypoxia or by inhibiting CBS via chemical or genetic means reduces persulfidation of PHD2 and inhibits activity, preventing hydroxylation of HIF-1α, resulting in stabilization. Our in vitro findings are further supported by the depletion of CBS in the zebrafish model that exhibits axis defects and abnormal intersegmental vessels. Exogenous H2S supplementation rescues both in vitro and in vivo phenotypes. We have identified the persulfidated residues and defined their functional significance in regulating the activity of PHD2 via point mutations. Thus, the CBS/H2S/PHD2 axis may provide therapeutic opportunities for pathologies associated with HIF-1α dysregulation in chronic diseases.

P1608Inhibition of GATA4 dimerization suppress hypertrophic responses

Introduction Hypertrophic signals eventually reach the nuclei of cardiomyocytes, change patterns of gene expression, and cause the development of heart failure. During the development of heart failure, intrinsic histone acetyltransferase called p300 induce GATA4 acetylation. Acetylated GATA4 increases its DNA binding, up-regulates cardiac hypertrophic response genes, and lead to heart failure. A zinc finger protein, GATA4 is the transcription factor that expression level is high in heart. It has been reported that GATA1, the same GATA family, regulates transcriptional activity through its homo-dimerization. However, GATA4 homo-dimerization and its relationship to hypertrophic responses are still unknown. Purpose To clarify the relationship between GATA4 homo-dimerization and transcriptional activity and investigate whether inhibition of this homo-dimerization become therapeutic target for cardiac hypertrophy. Methods GST pull-down and DNA pull-down assay were performed using GST fusion full length and deletion mutants of GATA4 and biotin-conjugated ET-1 promoter probe including a GATA element. Recombinant C-zinc finger domain (256–326), including C-zinc finger motif (256–295) and acetylation site (308–326) was cross-linked using glutaraldehyde and subjected to silver staining. An expression plasmid with three GATA4-acetylation site mutant-conjugated with nuclear localization sequence (3xG4D) was constructed. Immunoprecipitation and western blotting were performed using nuclear extract from HEK293T cells expressing p300, GATA4, and 3xG4D. Luciferase assay was using ANF and ET-1 promoter sequences. Neonatal rat cultured cardiomyocyte expressed 3xG4D and then stimulated with phenylephrine (PE) for 48 hours. Next cardiomyocytes stained with α-actinin antibody and measured the cell surface area. Results The acetylation site of GATA4 was required for the dimerization of GATA4. But, C-zinc finger motif (256–295) and the acetylation site were required for the DNA binding. Recombinant C-zinc finger domain formed not only a homo-dimer but also a multimer. Co-expression of p300 increased the formation of homo-dimer as well as the acetylation of GATA4 in HEK293T cells. The GATA4 homo-dimer was disrupted by acetyl-deficient GATA4 or HAT-deficient p300 mutant. Overexpression of 3xG4D prevented the dimerization of GATA4, but not acetylation of GATA4. The result of luciferase assay showed that overexpression of 3xG4D prevented p300/GATA-induced ANF and ET-1 promoter activities. Furthermore, overexpression of 3xG4D inhibited phenylephrine-induced cardiomyocyte hypertrophy. Conclusions These results suggest that GATA4 dimerization may play an important role in hypertrophy-response gene activation. Thus, it is likely that inhabitation of GATA4 dimerization become therapeutic target for cardiac hypertrophy.

Integrity of zinc finger motifs in PML protein is necessary for inducing its degradation by antimony

The presence of zinc ions in a zinc finger motif of a PML protein is a fundamental requirement for the protein's degradation by antimony.

The N-Terminal CCHC Zinc Finger Motif Mediates Homodimerization of Transcription Factor BCL11B

ABSTRACT The BCL11B gene encodes a Krüppel-like, sequence-specific zinc finger (ZF) transcription factor that acts as either a repressor or an activator, depending on its posttranslational modifications. The importance of BCL11B in numerous biological processes in multiple organs has been well established in mouse knockout models. The phenotype of the first de novo monoallelic germ line missense mutation in the BCL11B gene (encoding N441K) strongly implies that the mutant protein acts in a dominant-negative manner by neutralizing the unaffected protein through the formation of a nonfunctional dimer. Using a Förster resonance energy transfer-assisted fluorescence-activated cell sorting (FACS-FRET) assay and affinity purification followed by mass spectrometry (AP-MS), we show that the N-terminal CCHC zinc finger motif is necessary and sufficient for the formation of the BCL11B dimer. Mutation of the CCHC ZF in BCL11B abolishes its transcription-regulatory activity. In addition, unlike wild-type BCL11B, this mutant is incapable of inducing cell cycle arrest and protecting against DNA damage-driven apoptosis. Our results confirm the BCL11B dimerization hypothesis and prove its importance for BCL11B function. By mapping the relevant regions to the CCHC domain, we describe a previously unidentified mechanism of transcription factor homodimerization.

Functional analyses of the CIF1-CIF2 complex in Trypanosoma brucei identify the structural motifs required for complex formation and cytokinesis

ABSTRACTCytokinesis in trypanosome occurs uni-directionally along the longitudinal axis from the cell anterior towards the cell posterior and requires a trypanosome-specific CIF1-CIF2 protein complex. However, little is known about the contribution of the structural motifs in CIF1 and CIF2 to complex assembly and cytokinesis. Here, we demonstrated that the two zinc-finger motifs but not the coiled-coil motif in CIF1 are required for interaction with the EF-hand motifs in CIF2. We further showed that localization of CIF1 depends on the coiled-coil motif and the first zinc-finger motif and that localization of CIF2 depends on the EF-hand motifs. Deletion of the coiled-coil motif and mutation of either zinc-finger motifs in CIF1 disrupted cytokinesis. Further, mutation of either zinc-finger motif in CIF1 mis-localized CIF2 to the cytosol and destabilized CIF2, whereas deletion of the coiled-coil motif in CIF1 spread CIF2 over to the new flagellum attachment zone and stabilized CIF2. Together, these results uncovered the requirement of the coiled-coil motif and zinc-finger motifs for CIF1 function in cytokinesis and for CIF2 localization and stability, providing structural insights into the functional interplay between the two cytokinesis regulators.