Production of sterile transcripts of C gamma genes in an IgM-producing human neoplastic B cell line that switches to IgG-producing cells.
A human neoplastic B cell line SSK41 that expresses IgM on its surface switches spontaneously to IgG-producing cells. The SSK41 line contains a single immunoglobulin heavy-chain locus, the constant region (C) genes of which retain the germline configuration. The IgG-producing SSK41 line was purified by sorting, and shown to have undergone S-S recombination with deletion of the C mu gene. This line produced secretory and membrane-bound forms of gamma-chain mRNA. From cDNA libraries of a mixed population of IgM+/IgG+ SSK41 cells, we have isolated cDNA clones encoding the mature membrane-bound and secretory forms of the mu and gamma 1 heavy chains, all of which share the same variable region sequence. cDNA clones containing the mature gamma 3 chain were identified as well. We also isolated cDNA clones containing C gamma 1 and C gamma 3 sterile transcripts from the SSK41 line. These sterile transcripts contained additional exon sequences designated 'I' which were localized upstream of the C gamma 1 and C gamma 3 switch regions and homologous to murine counterparts. The I sequences were precisely spliced to the 5' ends of the corresponding C gamma exon sequences. These features of germline CH transcripts, i.e. the isotype specificity to class switching, location of exons, and sequences per se, are highly conserved between man and mouse.
Sideras
P
P
Department of Medical Chemistry, Faculty of Medicine, Kyoto University, Japan.
Mizuta
T R
TR
Kanamori
H
H
Suzuki
N
N
Okamoto
M
M
Kuze
K
K
Ohno
H
H
Doi
S
S
Fukuhara
S
S
Hassan
M S
MS
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D005803:Genes, Immunoglobulin; D005812:Genes, Switch; D006801:Humans; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D007134:Immunoglobulin Switch Region / Q000235:genetics; D007142:Immunoglobulin gamma-Chains / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured / Q000276:immunology
D007127:Immunoglobulin Constant Regions; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D007142:Immunoglobulin gamma-Chains; D012333:RNA, Messenger