Abstract
Using a 15-nucleotide primer specific for the immunoglobulin kappa-chain gene, we synthesized cDNA from the mRNA of an anti-alpha(1----6)dextran hybridoma. The hybridoma had been produced using MPC-11 as the parental myeloma. Hybridization and sequence analysis of one clone showed that it was derived from a 1.2-kilobase (kb) kappa-chain mRNA that lacked a joining minigene segment (J). The mRNA had the leader region correctly spliced to the variable region (V) but, in the absence of a J, V kappa was flanked by 62 nucleotides (3202-3263) from the intervening sequence (between J5 and the kappa-chain constant region gene C kappa) before being spliced to C kappa. This mRNA originated from the kappa-chain-fragment gene of MPC-11 but differed from the previously described 0.8-kb kappa-chain-fragment mRNA [Choi, E., Kuehl, W.M. & Wall, R. (1980) Nature (London) 286, 776-779; Seidman, J.G. & Leder, P. (1980) Nature (London) 286, 779-783] in which the leader sequence is spliced directly to C kappa. This 1.2-kb mRNA was present as a polyadenylylated species in total cellular RNA but could not be detected in cytoplasmic RNA. Thus, it either failed to be transported out of the nucleus or was rapidly degraded in the cytoplasm. These studies show that transcripts of the kappa-chain-fragment gene are processed by two distinct splicing pathways to yield either a 0.8-kb mRNA with the leader region spliced directly to C kappa or a 1.2-kb mRNA with leader, V, 62 nucleotides of the intervening sequence, and C kappa.