Ectopic T cell receptor-α locus control region activity in B cells is suppressed by direct linkage to two flanking genes at once.
The molecular mechanisms regulating the activity of the TCRα gene are required for the production of the circulating T cell repertoire. Elements of the mouse TCRα locus control region (LCR) play a role in these processes. We previously reported that TCRα LCR DNA supports a gene expression pattern that mimics proper thymus-stage, TCRα gene-like developmental regulation. It also produces transcription of linked reporter genes in peripheral T cells. However, TCRα LCR-driven transgenes display ectopic transcription in B cells in multiple reporter gene systems. The reasons for this important deviation from the normal TCRα gene regulation pattern are unclear. In its natural locus, two genes flank the TCRα LCR, TCRα (upstream) and Dad1 (downstream). We investigated the significance of this gene arrangement to TCRα LCR activity by examining transgenic mice bearing a construct where the LCR was flanked by two separate reporter genes. Surprisingly, the presence of a second, distinct, reporter gene downstream of the LCR virtually eliminated the ectopic B cell expression of the upstream reporter observed in earlier studies. Downstream reporter gene activity was unaffected by the presence of a second gene upstream of the LCR. Our findings indicate that a gene arrangement in which the TCRα LCR is flanked by two distinct transcription units helps to restrict its activity, selectively, on its 5'-flanking gene, the natural TCRα gene position with respect to the LCR. Consistent with these findings, a TCRα/Dad1 locus bacterial artificial chromosome dual-reporter construct did not display the ectopic upstream (TCRα) reporter expression in B cells previously reported for single TCRα transgenes.
Department of Biological Sciences, City University of New York, Hunter College, New York, New York, USA.
Stefan
S
Knirr
Janette
J
Gomos-Klein
Blanca E
BE
Andino
Faith
F
Harrow
Karl F
KF
Erhard
Damian
D
Kovalovsky
Derek B
DB
Sant'Angelo
Benjamin D
BD
Ortiz
D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001402:B-Lymphocytes / Q000378:metabolism*; D018801:CD2 Antigens / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D015793:HLA-B7 Antigen / Q000235:genetics / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D019901:Locus Control Region / Q000235:genetics*; D008221:Lymphoid Tissue / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic / Q000235:genetics; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism
D051017:Apoptosis Regulatory Proteins; D018801:CD2 Antigens; C083331:DAD1 protein, human; D015793:HLA-B7 Antigen; D006657:Histones; D008565:Membrane Proteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D008239:Lysine