title: HsOrc4-Dependent Dna Remodeling of the ori-β Dhfr Replicator.
abstract: Replication of DNA in multicellular organisms initiates from origin of replication (ori) sequences, which significantly differ in length and complexity. One of the best characterized is hamster dihydrofolate reductase (DHFR), which contains the ori-β sequence with several functionally relevant domains, such as an AT-rich region, dinucleotide repeat element (DNR), sequence-induced bend DNA (BEND) and a RIP60 protein-binding site (RIP60). Prior to initiation, ori sequences are recognized by origin recognition complex (ORC), which is a hetero hexamer complex that serves as the landing pad for proteins of the pre-replication complex. The function of each ORC subunit is still unclear. In this study, we analyze the function of subunit 4 of the human ORC complex (HsOrc4) in interaction with a plasmid bearing the ori-β DHFR sequence. We show that the topologically closed DHFR ori-β replicator contains a bubble-like structure within its AT-rich region and that it is reversibly modified in the interaction with HsOrc4. The non-canonical structure of the AT-rich region in the topologically closed ori sequence is recognized and changed by HsOrc4 using the energy of supercoiled DNA. These findings could help to further elucidate DNA replication and its possible association with human genetic diseases.
authors.forename: Branko
authors.initials: B
authors.lastname: Tomic
authors.forename: Jelena
authors.initials: J
authors.lastname: Kusic-Tisma
mesh_terms: D020856:AT Rich Sequence; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000378:metabolism; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003412:Cricetulus; D004261:DNA Replication; D004268:DNA-Binding Proteins; D009690:Nucleic Acid Conformation; D051738:Origin Recognition Complex / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D010957:Plasmids / Q000737:chemistry / Q000235:genetics; D016601:RNA-Binding Proteins; D018741:Replication Origin; D015719:Single-Strand Specific DNA and RNA Endonucleases / Q000737:chemistry / Q000378:metabolism; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*
chemical_list: D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C526101:Mung Bean Nuclease; C109152:ORC4 protein, human; D051738:Origin Recognition Complex; D010940:Plant Proteins; C404766:REPIN1 protein, human; D016601:RNA-Binding Proteins; D013762:Tetrahydrofolate Dehydrogenase; D015719:Single-Strand Specific DNA and RNA Endonucleases