Chen et al. (1998) determined the crystal structure of the DNA complex of a 67-kD core fragment of the STAT1 homodimer, lacking only the N-domain and the C-terminal transcriptional activation domain, at 2.9-angstrom resolution. Phosphorylation of Signal Transducer and Activator of transcription 1(STAT 1) was also decreased in rheumatoid arthritis lymphocytes. The transcription factor signal transducer and activator of transcription-1 (STAT1) plays a key role in immunity against mycobacterial and viral infections. Activation of the signal transducers and activators of transcription (STAT) pathway is important in fibroblast growth factor (FGF) modulation of chondrocyte proliferation and endochondral bone formation during embryogenesis.