Spotting new DNA damage-responsive chromatin-binding proteins.

In response to DNA damage, cells initiate multiple repair mechanisms that all contribute to the survival of both the cell and the organism. These responses are numerous and variable, and can include cell cycle arrest, transcriptional activation of DNA repair genes and relocalization of repair proteins to sites of DNA damage. If all else fails, in multicellular organisms the initiation of apoptosis is also a potential cellular response to DNA damage.

Structure of Alba: an archaeal chromatin protein modulated by acetylation.

Eukaryotic DNA is packaged into nucleosomes that regulate the accessibility of the genome to replication, transcription and repair factors. Chromatin accessibility is controlled by histone modifications including acetylation and methylation. Archaea possess eukary otic-like machineries for DNA replication, transcription and information processing.

The interaction of Alba, a conserved archaeal chromatin protein, with Sir2 and its regulation by acetylation.

The conserved Sir2 family of proteins has protein deacetylase activity that is dependent on NAD (the oxidized form of nicotinamide adenine dinucleotide). Although histones are one likely target for the enzymatic activity of eukaryotic Sir2 proteins, little is known about the substrates and roles of prokaryotic Sir2 homologs. We reveal that an archaeal Sir2 homolog interacts specifically with the major archaeal chromatin protein, Alba, and that Alba exists in acetylated and nonacetylated forms.

Preliminary crystallographic studies of the double-stranded DNA-binding protein Sso10b from Sulfolobus solfataricus.

Crystals of Sso10b from the hyperthermophilic archaeon Sulfolobus solfataricus have been grown that diffract to 2.6 A resolution. The protein is a highly abundant non-specific double-stranded DNA-binding protein, conserved throughout the archaea, that has been implicated in playing a role in the architecture of archaeal chromatin.

Holliday junction resolution is modulated by archaeal chromatin components in vitro.

The Holliday junction-resolving enzyme Hjc is conserved in the archaea and probably plays a role analogous to that of Escherichia coli RuvC in the pathway of homologous recombination. Hjc specifically recognizes four-way DNA junctions, cleaving them without sequence preference to generate recombinant DNA duplex products. Hjc imposes an X-shaped global conformation on the bound DNA junction and distorts base stacking around the point of cleavage, three nucleotides 3' of the junction center.