Unusual forms of T cell γ mRNA in a human T cell leukemia cell line: Implications for γ gene expression

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Abstract
The expression and rearrangement of T cell rearranging (TRG) γ genes in human leukemic cell lines has been examined. The cell line MOLT-17 produces abundant γ mRNA which is translated into a protein found on the cell surface which is associated with the CD3 molecule. The analysis of the γ mRNA sequences in MOLT-17, by cDNA cloning, shows transcripts of aberrantly rearranged genes as well as the productively rearranged allele. The productive allele consists of a rearranged V 8 gene joined to Jγ2. Two forms of aberrant transcript originate from the other rearranged γ allele. One of these initiates just upstream of the unrearranged Jγ2 segment, and the other initiates from a Vγ8 gene segment joined to another Jγ segment, upstream of Jγ2. An unusual feature of the latter transcript is that polyadenlyation has occurred at the end of the first exon of Cγ2, where two conserved poly(A) addition signals occur. The MOLT-4 cell line, on the other hand, has productively and nonproductively rearranged γ alleles, from which relatively little transcription occurs. These results define new Jγ segments in the human TRG γ locus and suggest that positive activation of the γ locus is necessary for high level transcription after rearrangement.