title: Crystal structure of a SeqA-N filament: implications for DNA replication and chromosome organization.
abstract: Escherichia coli SeqA binds clusters of transiently hemimethylated GATC sequences and sequesters the origin of replication, oriC, from methylation and premature reinitiation. Besides oriC, SeqA binds and organizes newly synthesized DNA at replication forks. Binding to multiple GATC sites is crucial for the formation of stable SeqA-DNA complexes. Here we report the crystal structure of the oligomerization domain of SeqA (SeqA-N). The structural unit of SeqA-N is a dimer, which oligomerizes to form a filament. Mutations that disrupt filament formation lead to asynchronous DNA replication, but the resulting SeqA dimer can still bind two GATC sites separated from 5 to 34 base pairs. Truncation of the linker between the oligomerization and DNA-binding domains restricts SeqA to bind two GATC sites separated by one or two full turns. We propose a model of a SeqA filament interacting with multiple GATC sites that accounts for both origin sequestration and chromosome organization.
authors.affiliation: Laboratory of Molecular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA. guarnea@mcmaster.ca
authors.forename: Alba
authors.initials: A
authors.lastname: Guarné
authors.forename: Therese
authors.initials: T
authors.lastname: Brendler
authors.forename: Qinghai
authors.initials: Q
authors.lastname: Zhao
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Ghirlando
authors.forename: Stuart
authors.initials: S
authors.lastname: Austin
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D020836:Protein Structure, Quaternary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C089746:SeqA protein, E coli; D004247:DNA