Structure and expression of the T cell receptor gamma locus in pre-B and early hemopoietic cells

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Abstract
The genetic structure and expression of the T cell receptor (TcR) loci were examined in pre-B and early hemopoietic cells. Thirty-eight percent of Abelson murine leukemia virus-transformed pre-B cell lines were rearranged at TcR.gamma.. Moreover, many pre-B cell lines were rearranged at two distinct .gamma. loci, V.gamma.1.2 and V.gamma.2. The .gamma. rearrangements in the pre-B cell lines were similar to those observed previously in T cell lines. V + C-containing .gamma. mRNA was detected in two pre-B cell lines. In all other pre-B and interleukin (IL) 3-dependent lymphoid and myeloid lines examined, smaller C.gamma.-containing mRNA were detected. These C.gamma. transcripts were independent of the genetic configuration of the .gamma. locus. In contrast, the TcR.alpha. and .beta. loci were in the germ-line configuration in all non-T cell lines examined and mRNA encoding these loci were not detected. When IL3-dependent lymphoid and myeloid cell lines were transformed to growth factor independence by a non-autocrine mechanism, no mRNA transcripts encoding TcR C.gamma. were detected. However, TcR C.gamma. mRNA transcripts were detected in factor-independent cell lines that arose by an autocrine mechanism. The cell cycle expression of C.gamma. was compared with protooncogenes and other marker genes previously shown to be cell cycle specific. mRNA transcripts encoding C.gamma. were detected in the highest amounts 4-8 h after IL3, but not phorbol myristate acetate, addition. A similar time period of expression was observed with ornithine decarboxylase which has been shown to be expressed in G1 phase. These observations indicate that TcR.gamma. is often rearranged in pre-B cell lines and may be directly regulated by IL3 in IL3-dependent cells.