Titration of repeat-induced point mutation (RIP) by chromosome segment duplications in Neurospora crassa.
Repeat-induced point mutation (RIP) is a hypermutational process that alters duplicated DNA sequences in Neurospora crassa. In previous studies, five of six large ( > 100 kb) chromosome segment duplications (Dp's) examined were shown to dominantly suppress RIP in smaller (< 5 kb) duplications. The suppressor duplications were > 270 kb, whereas the lone non-suppressor duplication was approximately 117 kb. We have now screened another 33 duplications and found 29 more suppressors and four more non-suppressors. All 22 suppressor duplications whose size could be estimated were > 270 kb, whereas two newly identified non-suppressor duplications examined were 140-154 kb. RIP was suppressed in a subset of crosses heterozygous for more than one ordinarily non-suppressor duplication. These results strengthen the hypothesis that large duplications titrate out the RIP machinery and suggest the "equivalence point" for the titration is close to 300 kb.
Singh
Parmit K
PK
Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India.
Kasbekar
Durgadas P
DP
D015825:Chromosomes, Fungal / Q000235:genetics*; D003433:Crosses, Genetic; D004271:DNA, Fungal / Q000235:genetics; D020440:Gene Duplication; D005799:Genes, Dominant; D005800:Genes, Fungal; D006579:Heterozygote; D009492:Neurospora crassa / Q000235:genetics*; D010641:Phenotype; D017354:Point Mutation
D004271:DNA, Fungal