title: Avoidance of base runs in switch regions of immune-system genes.
abstract: Mouse immunoglobulin (Ig) switch-region sequences are anti-"runny"; that is, they have a smaller amount of their total bases in homonucleotide tracts ("runs") than would be expected if each nucleotide in the sequence were a random selection from a pool of the composition of the region. The switch sequences involve the first intron of rearranged Ig heavy-chain genes; this intron differs strikingly from the succeeding ones, which are "runny" (have more bases than expected in runs). Switch regions are the only category of sequences so far found to be antirunny by statistical test. This sequence characteristic is related to the presence in switch sequences of repeating heteronucleotides. We suggest that the resulting base dispersion and increased complexity favor more specific interactions between sequences, which may be advantageous in recombinational processes such as switching and translocation.
mesh_terms: D000818:Animals; D001483:Base Sequence; D005803:Genes, Immunoglobulin; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007134:Immunoglobulin Switch Region / Q000235:genetics*; D008223:Lymphoma / Q000235:genetics; D008969:Molecular Sequence Data; D009857:Oncogenes; D011518:Proto-Oncogene Proteins / Q000235:genetics; D016271:Proto-Oncogene Proteins c-myc; D011995:Recombination, Genetic; D014178:Translocation, Genetic; D014714:Vertebrates / Q000235:genetics
chemical_list: D007143:Immunoglobulin Heavy Chains; D011518:Proto-Oncogene Proteins; D016271:Proto-Oncogene Proteins c-myc