PJA-BP expression and TCR delta deletion during human T cell differentiation

Recombination of deltaRec to psiJalpha will delete the TCR delta gene,which is thought to play an important role in the bifurcation of the TCRalphabeta versus TCR gammadelta differentiation lineages. We recentlydetected a DNA-binding protein in human thymocytes, the so- called PJA-BP,which recognizes the psiJalpha gene segment and might be one of the factorsinvolved in the regulation of preferential deltaRec- psiJalpharearrangements. We now investigate PJA-BP expression and its correlationwith TCR delta gene deletion in thymocytes. Our electrophoretic mobilityshift assay experiments showed that the PJA-BP is evolutionary conserved inhuman, murine and simian thymocytes. Using a large series of humanhematopoietic malignancies (n = 30), we conclude that PJA-BP expression isthymocyte specific and seems to be restricted to thymocytes committed tothe TCR alphabeta lineage. Analysis of seven well-defined human thymocytesubpopulations showed that preferential deltaRec-psiJalpha rearrangementsas well as PJA-BP expression can be detected from the immatureCD34-/CD1+/CD3- /CD4+/CD8alpha+beta- thymocyte differentiation stageonwards. These experiments indicate that expression of PJA-BP in humanthymocytes starts simultaneously with preferential deltaRec-psiJalpharearrangements, which supports our hypothesis that PJA-BP is one of thefactors involved in the preferential recombination of deltaRec topsiJalpha.