title: On immunoglobulin heavy chain gene switching: two gamma 2b genes are rearranged via switch sequences in MPC-11 cells but only one is expressed.
abstract: During B lymphocytes differentiation, switches in the expression of heavy chain immunoglobulin constant region (CH) genes occur by a novel DNA recombination mechanism. We have investigated the requirements of the CH gene switch  by characterizing two rearranged gamma 2b genes from a gamma 2b producing mouse myeloma (MPC-11). One of the two gamma 2b genes is present in 2-3 copies per cell (gamma 2b strong hybridizer) while the other is present in approximately 1 copy per cell (gamma 2b weak hybridizer). Genomic clones of the gamma 2b strongly hybridizing gene indicate that this is an abortive switch event between the S gamma 3 and S gamma 2b regions. However, clones of the gamma 2b weakly hybridizing gene suggest a functional rearrangement due to the presence of VH, JH and S mu sequences. The switch-recombination sites of these rearranged gamma 2b genes and those of other CH genes show a high degree of preference for the sequence AGGTTG 5' of either the S mu donor site or the appropriate CH S acceptor site. AGGTTG and its analogs are rare in the S mu region, are somewhat prevalent in s alpha and in the case of S mu are found 5' of a tandemly repeated DNA sequence (GAGCT, GGGGT) comprising most of S mu.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005796:Genes; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D009693:Nucleic Acid Hybridization; D010954:Plasmacytoma; D010957:Plasmids; D014158:Transcription, Genetic
chemical_list: D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007136:Immunoglobulins; D004262:DNA Restriction Enzymes