Project description:Pili on the surface of Sulfolobus islandicus are used for a host of functions, and serve as receptors for certain archaeal viruses. We find that these pili, when removed from cells, resist digestion by trypsin or pepsin, and survive boiling in SDS or 5M guanidinium-HCl. We have used cryo-EM to determine the structure of these filaments at 4.1 Å resolution. An atomic model was built by combining the map with bioinformatics without prior knowledge of the pilin sequence, an approach that should prove useful when looking at assemblies where all of the components may not be known. The atomic structure of the archaeal pilus was unusual due to almost a third of the residues being either threonine or serine and many hydrophobic surface residues. While the map showed specific glycosylation of only three residues, mass per unit length measurements suggested extensive glycosylation. We show that this extensive glycosylation renders these filaments soluble and provides the remarkable structural stability. We also show that the overall fold of the archaeal pilin is quite similar to archaeal flagellin, establishing common evolutionary origins.
Project description:We use MNase-Seq to elucidate primary chromatin architecture in an archaeon without histones, the acido-thermophilic archaeon Thermoplasma acidophilum. Like all members of the Thermoplasmatales, T. acidophilum harbours a HU family protein, HTa, that is highly expressed and protects - like histones but unlike well-characterized bacterial HU proteins – a sizeable fraction of the genome from MNase digestion. Comparing HTa-based chromatin architecture to that of three histone-encoding archaea, Methanothermus fervidus, Haloferax volcanii, and Thermococcus kodakkarensis, we present evidence that HTa is an archaeal histone analog. HTa-protected fragments are GC-rich, display histone-like mono- and dinucleotide patterns around the dyad, exhibit relatively invariant positioning throughout the growth cycle, and show archaeal histone-like oligomerization dynamics. Our results suggest that HTa, a DNA-binding protein of bacterial origin, has converged onto an architectural role filled by histones in other archaea.
Project description:We use MNase-Seq to elucidate primary chromatin architecture in an archaeon without histones, the acido-thermophilic archaeon Thermoplasma acidophilum. Like all members of the Thermoplasmatales, T. acidophilum harbours a HU family protein, HTa, that is highly expressed and protects - like histones but unlike well-characterized bacterial HU proteins – a sizeable fraction of the genome from MNase digestion. Comparing HTa-based chromatin architecture to that of three histone-encoding archaea, Methanothermus fervidus, Haloferax volcanii, and Thermococcus kodakkarensis, we present evidence that HTa is an archaeal histone analog. HTa-protected fragments are GC-rich, display histone-like mono- and dinucleotide patterns around the dyad, exhibit relatively invariant positioning throughout the growth cycle, and show archaeal histone-like oligomerization dynamics. Our results suggest that HTa, a DNA-binding protein of bacterial origin, has converged onto an architectural role filled by histones in other archaea.
Project description:Despite knowledge of complex prokaryotic transcription mechanisms, generalized rules, such as the simplified organization of genes into operons with well-defined promoters and terminators, have played a significant role in systems analysis of regulatory logic in both bacteria and archaea. Here, we have investigated the prevalence of alternate regulatory mechanisms through genome-wide characterization of transcript structures of ~64% of all genes including putative non-coding RNAs in Halobacterium salinarum NRC-1. Our integrative analysis of transcriptome dynamics and protein-DNA interaction datasets revealed widespread environment-dependent modulation of operon architectures, transcription initiation and termination inside coding sequences, and extensive overlap in 3' ends of transcripts for many convergently transcribed genes. A significant fraction of these alternate transcriptional events correlate to binding locations of 11 transcription factors and regulators (TFs) inside operons and annotated genes - events usually considered spurious or non-functional. With experimental validation, we illustrate the prevalence of overlapping genomic signals in archaeal transcription, casting doubt on the general perception of rigid boundaries between coding sequences and regulatory elements This SuperSeries is composed of the SubSeries listed below.
Project description:Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription. Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription.
Project description:Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription. Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription.
Project description:This SuperSeries is composed of the following subset Series: GSE12923: Halobacterium salinarum NRC-1 growth curve, tiling arrays. GSE12977: Halobacterium salinarum NRC-1 growth curve GSE13108: Halobacterium salinarum NRC-1 conditional ChIP-chip for transcription initiation factor IIB 4 (TFBd) GSE7045: ChIP-Chip of General Transcription factors in Halobacterium NRC-1 GSE15786: Halobacterium sp. NRC-1 ChIP-chip for TFBa, TFBd and TFBf, high resolution array GSE15788: Halobacterium salinarum NRC-1 total RNA hybridization of TFBd overexpression versus Reference sample Despite knowledge of complex prokaryotic transcription mechanisms, generalized rules, such as the simplified organization of genes into operons with well-defined promoters and terminators, have played a significant role in systems analysis of regulatory logic in both bacteria and archaea. Here, we have investigated the prevalence of alternate regulatory mechanisms through genome-wide characterization of transcript structures of ~64% of all genes including putative non-coding RNAs in Halobacterium salinarum NRC-1. Our integrative analysis of transcriptome dynamics and protein-DNA interaction datasets revealed widespread environment-dependent modulation of operon architectures, transcription initiation and termination inside coding sequences, and extensive overlap in 3' ends of transcripts for many convergently transcribed genes. A significant fraction of these alternate transcriptional events correlate to binding locations of 11 transcription factors and regulators (TFs) inside operons and annotated genes - events usually considered spurious or non-functional. With experimental validation, we illustrate the prevalence of overlapping genomic signals in archaeal transcription, casting doubt on the general perception of rigid boundaries between coding sequences and regulatory elements Refer to individual Series
Project description:Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription. Since their discovery, archaea have not only proven a fascinating domain in their own right, but also helped us understand the evolution and function of molecular components they share with bacteria or eukaryotes. Archaeal histones are homologous to their eukaryotic counterparts, but operate in a less constrained bacterial-like cellular environment and their role in transcription and genome function remains obscure. In order to understand how archaeal histones affect transcriptional processes, we induced expression of the two histones from the archaeon Methanothermus fervidus in a naive bacterial system (E. coli) that has not evolved to integrate this kind of proteins. We show, using a series of MNase digestion experiments, that these histones bind the bacterial genome and wrap DNA in vivo in a pattern consistent with a previously proposed multimerisation model, in a similar pattern observed natively. We correlate genome-wide occupancy maps and gene expression profiles in different phases of growth to show that – although expression of archaeal histones triggers morphological changes in E. coli – there appears to only be an indirect effect on transcription.