Nuclear reprogramming can be defined as a change in nuclear function. Nuclear transplantation studies indicate that nuclear reprogramming is possible. However, ethical issues and availability of materials resulting from embryo cloning are significant limi tations for investigating mechanisms of reprogramming. Based on recent preliminary data, we propose a novel in vitro nuclear reprogramming technology to modulate the cell program and investigate how nuclear reprogramming takes place. We will develop an ex tract from activated T cells that promotes chromatin-binding of T cell-specific transcription factors in heterologous nuclei, remodel chromatin and activate the dormant interleukin-2 (IL-2) gene. Markers of reprogramming to be investi gated, including (1) chromatin-binding of transcriptional regulators of the IL-2 gene in heterologous (B cell, fibroblast, endothelial) nuclei; (2) chromatin remodeling at the IL-2 locus, including changes in histone acetylation, and activity of the chrom atin remodeling com plex, SWI/SNF; (3) activation of silent genes in the reprogrammed nuclei using DNA arrays. In vitro reprogramming presents commercial, societal and technological benefits. It has applications in the development of novel cell therapeutics, elimination of d isease genes, production of large numbers of reprogrammed nuclei for proteomic studies. It also alleviates ethical issues because no embryo cloning is performed for reprogramming.