DNA sequence of the murine gamma 1 switch segment reveals novel structural elements.

摘要: Immunoglobulin heavy chain switch regions are segments of DNA considered to be important in mediating class switching B lymphocytes. Whereas these vary length among the different murine isotypes, their structural organization schemes all based on tandem repetition unit sequences. We previously showed that S gamma 1 segment unexpectedly contains sequence elements differ significantly from its prevalent repeat (49mer). Here we extend this preliminary characterization by determining complete nucleotide cloned BALB/c DNA. find consists more than 120 tandemly repeated 49mers. In addition, show identified non-49mer sequences part a direct element about 350 bp (DR II), which exists two copies at 5' end 1. also another unrelated 500 long I) near and 3' ends Thus, structure might may abbreviated as 5'-DRII-(49mer)15-DRI-DRII-(49mer)n-DRI , where n is between 40 160. Our results Southern hybridization experiments suggest basic scheme maintained eight Igh haplotypes, although haplotypes include numbers 49mer elements. Other size various loci, but lesser extent At level sequences, 1, 3, 2b represent three distinct, nonoverlapping sets