Unusual forms of T cell gamma mRNA in a human T cell leukemia cell line: implications for gamma gene expression.

The expression and rearrangement of T cell rearranging (TRG) gamma genes in human leukemic cell lines has been examined. The cell line MOLT-17 produces abundant gamma mRNA which is translated into a protein found on the cell surface which is associated with the CD3 molecule. The analysis of the gamma 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 gamma 8 gene joined to J gamma 2. Two forms of aberrant transcript originate from the other rearranged gamma allele. One of these initiates just upstream of the unrearranged J gamma 2 segment, and the other initiates from a V gamma 8 gene segment joined to another J gamma segment, upstream of J gamma 2. An unusual feature of the latter transcript is that polyadenlyation has occurred at the end of the first exon of C gamma 2, where two conserved poly(A) addition signals occur. The MOLT-4 cell line, on the other hand, has productively and nonproductively rearranged gamma alleles, from which relatively little transcription occurs. These results define new J gamma segments in the human TRG gamma locus and suggest that positive activation of the gamma locus is necessary for high level transcription after rearrangement.