Lymphoid-specific transcription mediated by the conserved octamer site: who is doing what?

The conserved octamer site found in the promoters of Immunoglobulin (Ig) genes has been identified early on as a key element for B cell-specific Ig promoter activity and has also been associated with expression of other B cell-specific genes. Several transcription factors--ubiquitous or cell-restricted--interact specifically with the octamer motif in B cells: Oct-1 and Oct-2 are POU domain transcription factors that bind directly to the octamer site and thereby can recruit the coactivator OBF-1 to the promoters of various genes. Yet, in spite of intense work, the precise role played by each of these factors for transcription activation through the octamer motif is unclear. In particular, genetic inactivation in mice of the lymphoid cell-specific transcription factor Oct-2 or of the B cell-specific coactivator OBF-1 led to surprising findings that are being discussed.