CRISP-3, A PROTEIN WITH HOMOLOGY TO PLANT DEFENSE PROTEINS, IS EXPRESSED IN MOUSE B-CELLS UNDER THE CONTROL OF OCT2

The Oct2 transcription factor is expressed throughout the B-lymphoid l ineage and plays an essential role during the terminal phase of B-cell differentiation. Several genes specifically expressed in B lymphocyte s have been identified that contain a functional octamer motif in thei r regulatory elements. However, expression of only a single gent, the murine CD36 gene, has been shown to date to be dependent on Oct2, Here , we present the identification and characterization of a further gene , coding For cysteine-rich secreted protein 3 (CRISP-3), whose express ion in B cells is regulated by Oct2. We show that CRISP-3 is expressed in the B-lymphoid lineage specifically at the pre-B-cell stage. By us ing different experimental strategies, including nuclear run-on experi ments, we demonstrate that this gene is transcriptionally activated bg Oct2. Furthermore, analysis of CR1SP-3 expression in primary B cells derived from either wild-type or Oct2-deficient mice demonstrates the dependence on Oct2, Two variant octamer motifs were identified in the upst ream promoter region of the crisp-3 gene, and Oct2 interacts with both of them in vitro. Cotransfection experiments with expression vec tors for Oc1 and Oct2 together with a reporter driven by the a crisp-3 promoter showed that transcriptional activation of this promoter can only be achieved with Oct2. The C-terminal transactivation domain of O ct2 is required for this activation, Finally, introducing specific mut ations in the tyro variant octamer motifs in revealed that both of the m are important for full transcriptional activation by Oct2.