Capture of cytokine-responsive genes (NACA and RBM3) using a gene trap approach

We have developed a gene trap approach to select specific cytokine receptor/ligand responsive genes in the cell line TF-1. This cell line exhibits a dependency on granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-3 (IL-3) and responds to interleukin-5 (IL-5). In an attempt to detect genes modulated by one of these factors, cells were infected with the Rosabetageo retrovirus in the presence of GM-CSF, IL-3, or IL-5 and clones were selected for retroviral integration on the basis of G418 resistance. Housekeeping and cytokine-regulated trapped genes were then differentiated on the basis of G418 resistance versus sensitivity in the presence of the different cytokines. To determine the reliability of this screen, DNA sequences upstream of the proviral integration site were identified by 5' rapid amplification of DNA ends polymerase chain reaction (RACE PCR) from selected GM-CSF-treated and -infected clones. Comparison of the sequences with those in the Genbank database revealed that 2 sequences correspond to known genes: NACA and RBM3. NACA was recently defined as a coactivator of c-jun-mediated transcription factors in osteoblasts, and RBM3 as a protein from the heterogeneous nuclear ribonucleoprotein family. Data from transcriptional analysis of these 2 genes in TF-1 cells showed a specific up-regulation by GM-CSF. Both transcripts were also found to be up-regulated in purified CD34(+) cells, suggesting their involvement in proliferative processes during hematopoiesis. Interestingly, down-regulation was observed during monocytic differentiation of TF-1 cells, suggesting their extinction could contribute to monocytic lineage development. This study demonstrates that this gene trap approach is a useful method for identifying novel, specific cytokine-responsive genes that are involved in the regulation of hematopoiesis. (Blood. 2000;95:3750-3757)