Direct recognition of homology between double helices of DNA in Neurospora crassa.
Chromosomal regions of identical or nearly identical DNA sequence can preferentially associate with one another in the apparent absence of DNA breakage. Molecular mechanism(s) underlying such homology-dependent pairing phenomena remain(s) unknown. Using Neurospora crassa repeat-induced point mutation (RIP) as a model system, we show that a pair of DNA segments can be recognized as homologous, if they share triplets of base pairs arrayed with the matching periodicity of 11 or 12 base pairs. This pattern suggests direct interactions between slightly underwound co-aligned DNA duplexes engaging once per turn and over many consecutive turns. The process occurs in the absence of MEI3, the only RAD51/DMC1 protein in N. crassa, demonstrating independence from the canonical homology recognition pathway. A new perspective is thus provided for further analysis of the breakage-independent recognition of homology that underlies RIP and, potentially, other processes where sequence-specific pairing of intact chromosomes is involved.
Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Room NW140, Cambridge, Massachusetts 02138, USA.
Eugene
E
Gladyshev
Department of Molecular and Cellular Biology, Harvard University, 52 Oxford Street, Room NW140, Cambridge, Massachusetts 02138, USA.
Nancy
N
Kleckner
D004271:DNA, Fungal / Q000737:chemistry* / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D009492:Neurospora crassa / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D009690:Nucleic Acid Conformation; D017354:Point Mutation; D012091:Repetitive Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid
D004271:DNA, Fungal; D005656:Fungal Proteins