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BUB1 is a budding yeast gene required to ensure that progression through mitosis is coupled to correct spindle assembly. Two related human protein kinases, Bub1 and BubR1, both localise to kinetochores during mitosis, suggesting that they play a role in delaying anaphase until all chromosomes achieve correct, bipolar attachment to the spindle. However, how(More)
Polycomb-repressive complex 1 (PRC1) has a central role in the regulation of heritable gene silencing during differentiation and development. PRC1 recruitment is generally attributed to interaction of the chromodomain of the core protein Polycomb with trimethyl histone H3K27 (H3K27me3), catalyzed by a second complex, PRC2. Unexpectedly we find that RING1B,(More)
The PspA protein, a negative regulator of the Escherichia coli phage shock psp operon, is produced when virulence factors are exported through secretins in many Gram-negative pathogenic bacteria and its homologue in plants, VIPP1, plays a critical role in thylakoid biogenesis, essential for photosynthesis. Activation of transcription by the(More)
The 25.3 kDa "adaptor" protein, PspA (phage shock protein A), is found in the cytoplasm and in association with the inner membrane of certain bacteria. PspA plays critical roles in negatively regulating the phage shock response and maintaining membrane integrity, especially during the export of proteins such as virulence factors. Homologues of PspA function(More)
The mechanisms by which the major Polycomb group (PcG) complexes PRC1 and PRC2 are recruited to target sites in vertebrate cells are not well understood. Building on recent studies that determined a reciprocal relationship between DNA methylation and Polycomb activity, we demonstrate that, in methylation-deficient embryonic stem cells (ESCs), CpG density(More)
The Escherichia coli phage shock protein system (pspABCDE operon and pspG gene) is induced by numerous stresses related to the membrane integrity state. Transcription of the psp genes requires the RNA polymerase containing the sigma(54) subunit and the AAA transcriptional activator PspF. PspF belongs to an atypical class of sigma(54) AAA activators in that(More)
Conformational changes in sigma 54 (sigma(54)) and sigma(54)-holoenzyme depend on nucleotide hydrolysis by an activator. We now show that sigma(54) and its holoenzyme bind to the central ATP-hydrolyzing domains of the transcriptional activators PspF and NifA in the presence of ADP-aluminum fluoride, an analog of ATP in the transition state for hydrolysis.(More)
Recent studies have shown that PRC1-like Polycomb repressor complexes monoubiquity-late chromatin on histone H2A at lysine residue 119. Here we have analyzed the function of the polycomb protein Mel-18. Using affinity-tagged human MEL-18, we identify a polycomb-like complex, melPRC1, containing the core PRC1 proteins, RING1/2, HPH2, and CBX8. We show that,(More)
An important facet of transcriptional repression by Polycomb repressive complex 1 (PRC1) is the mono-ubiquitination of histone H2A by the combined action of the Posterior sex combs (Psc) and Sex combs extra (Sce) proteins. Here, we report that two ubiquitin-specific proteases, USP7 and USP11, co-purify with human PRC1-type complexes through direct(More)
The histone fold is a structural motif with which two related proteins interact and is found in complexes involved in wrapping DNA, the nucleosome, and transcriptional regulation, as in NC2. We reveal a novel function for histone-fold proteins: facilitation of nucleosome remodeling. ACF1-ISWI complex (ATP-dependent chromatin assembly and remodeling factor(More)