Xz. Deng et al., CHARACTERIZATION OF HUMAN TCR V-BETA GENE PROMOTER - ROLE OF THE DODECAMER MOTIF IN PROMOTER ACTIVITY, The Journal of biological chemistry, 273(37), 1998, pp. 23709-23715
During T-lymphocyte development, the T-cell antigen receptor (TCR) gen
e expression is controlled by its promoter and enhancer elements and r
egulated in tissue and development stage-specific manner. To uncover t
he promoter function and to define positive and negative regulatory el
ements in TCR gene promoters, the promoter activities from 13 human TC
R V beta genes were determined by the transient transfection system an
d luciferase reporter assay. Although most of the TCR V beta gene prom
oters that we tested are inactive by themselves, some promoters were f
ound to be constitutively strong. Among them, V beta 6.7 is the strong
est. 5'-Deletion and fragmentation experiments have narrowed the full
promoter activity of V beta 6.7 to a fragment of 147 base pairs immedi
ately 5' to the transcription initiation site. A decanucleotide motif
with the consensus sequence AGTGAYRTCA has been found to be conserved
in most TCR V beta gene promoters. There are three such decamer motifs
in the promoter region of V beta 6.7, and the contribution of each su
ch motif to the promoter activity has been examined. Further site-dire
cted mutagenesis analyses showed that: 1) when two Ts in the decamer w
ere mutated, the promoter activity was totally abolished; 2) when two
additional nucleotides 3' to the end of decamer were mutated, the prom
oter activity was decreased to two-thirds of the full level; and 3) wh
en the element with the sequence AGTGATGTCACT was inserted into other
promoters, the original weak promoters become very strong. Taken toget
her, our data suggest that the positive regulatory element in V beta 6
.7 should be considered a dodecamer rather than a decamer and that it
confers strong basal transcriptional activity on TCR VP genes.