title: Molecular visualization of immunoglobulin switch region RNA/DNA complex by atomic force microscope.
abstract: Immunoglobulin heavy-chain (IgH) class switch recombination (CSR) is initiated by DNA breakage in the switch (S) region featuring tandem repetitive nucleotide sequences. Various studies have demonstrated that S-region transcription and splicing proceed to genomic recombination and are indispensable for CSR in vivo, although the precise molecular mechanism is largely unknown. Here, we show the novel physical property of the in vitro transcribed S-region RNA by direct visualization using an atomic force microscope (AFM). The S-region sense RNA, but not the antisense RNA, forms a persistent hybrid with the template plasmid DNA and changes the plasmid conformation from supercoil to open circle in the presence of spermidine. In addition, the S-region transcripts generate globular forms and are assembled on the template DNA into a large aggregate that may stall replication and increase the recombinogenicity of the S-region DNA.
authors.affiliation: Research Institute for Biological Sciences, Tokyo University of Science, 2669 Yamazaki, Noda, Chiba 278-0022, Japan. mizuta@rs.noda.tus.ac.jp
authors.forename: Ryushin
authors.initials: R
authors.lastname: Mizuta
authors.forename: Kousuke
authors.initials: K
authors.lastname: Iwai
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Shigeno
authors.forename: Midori
authors.initials: M
authors.lastname: Mizuta
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uemura
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Ushiki
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kitamura
mesh_terms: D017578:Immunoglobulin Class Switching; D018625:Microscopy, Atomic Force; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure*; D012313:RNA / Q000737:chemistry / Q000235:genetics* / Q000648:ultrastructure*; D014158:Transcription, Genetic
chemical_list: D012313:RNA