Genes encoding Xenopus laevis Ig L chains. Implications for the evolution of kappa and lambda chains.
Xenopus laevis Ig contain two distinct types of L chains, designated rho or L1 and sigma or L2. We have analyzed Xenopus genomic DNA by Southern blotting with cDNA probes specific for L1 V and C regions. Many fragments hybridized to the V probe, but only one or two fragments hybridized to the C probe. Corresponding C, J, and V gene segments were identified on clones isolated from a genomic library prepared from the same DNA. One clone contains a C gene segment separated from a J gene segment by an intron of 3.4 kb. The J and C gene segments are nearly identical in sequence to cDNA clones analyzed previously. The C segment is somewhat more similar and the J segment considerably more similar in sequence to the corresponding segments of mammalian kappa chains than to those of mammalian lambda chains. Upstream of the J segment is a typical recombination signal sequence with a spacer of 23 bp, as in J kappa. A second clone from the library contains four V gene segments, separated by 2.1 to 3.6 kb. Two of these, V1 and V3, have the expected structural and regulatory features of V genes, and are very similar in sequence to each other and to mammalian V kappa. A third gene segment, V2, resembles V1 and V3 in its coding region and nearby 5'-flanking region, but diverges in sequence 5' to position -95 with loss of the octamer promoter element. The fourth V-like segment is similar to the others at the 3'-end, but upstream of codon 64 bears no resemblance in sequence to any Ig V region. All four V segments have typical recombination signal sequences with 12-bp spacers at their 3'-ends, as in V kappa. Taken together, the data suggest that Xenopus L1 L chain genes are members of the kappa gene family.
Zezza
D J
DJ
Department of Biology, Massachusetts Institute of Technology, Cambridge 02139.
Stewart
S E
SE
Steiner
L A
LA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D004247:DNA / Q000032:analysis; D015723:Gene Library; D005803:Genes, Immunoglobulin; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007133:Immunoglobulin Joining Region / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics; D007145:Immunoglobulin kappa-Chains / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D015183:Restriction Mapping; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014982:Xenopus laevis / Q000235:genetics*
D007127:Immunoglobulin Constant Regions; D007133:Immunoglobulin Joining Region; D007147:Immunoglobulin Light Chains; D007135:Immunoglobulin Variable Region; D007145:Immunoglobulin kappa-Chains; D004247:DNA