Analysis of the methylation state of the T cell receptor beta chain gene in T cells and large granular lymphocytes.

We have evaluated the methylation state of the T cell receptor beta chain gene (TcR beta) in freshly isolated human large granular lymphocyte (LGL) and T cell DNA in order to investigate the relationship between LGL and T cells with regard to methylation of this region of genomic DNA. In addition, we wished to determine whether hypomethylation of specific regions of the beta chain gene DNA might account for the production of only a nonfunctional 1.0-kilobase (kb) TcR beta mRNA transcript in LGL. Our analysis indicates that the heterogeneous pattern of methylation seen in LGL DNA lies predominantly in the J beta 1 region of the TcR beta DNA structure. The CCGG sequences located at the beginning of the HTF island (CG-rich region) in the J beta 2 region are nonmethylated in both LGL and at least half of the T cell DNA, suggesting that the HTF island is nonmethylated in both LGL and T cell DNA. In addition, specific methylation differences between T cell and LGL DNA can be detected 0.7 kb 3' to the last exon of C beta 1, just 5' to the first exon and within the second exon of the C beta 2 region. The heterogeneous methylation state of the TcR beta J beta 1 region in LGL DNA may be due to and a result of the differential use of the J beta 1 segment for generation of the nonfunctional 1.0-kb mRNA in LGL. These results and our previous studies (Sakamoto, S., Ortaldo, J. R., and Young, H. A. (1988) J. Immunol. 140, 654-660 and Sakamoto, S., and Young, H. A. (1988) Nucleic Acid Res. 16, 2149-2163) indicate that DNA methylation may be one method by which functional gene expression is controlled in specific lymphoid cell populations.