The functional anatomy of kappa promoters

Immunoglobulin kappa promoters were collected from mice and man. It was shown that they had homology within but not between subgroups, and the promoters were also conserved between species. The octamer element was found in all promoters, but other sequence elements were conserved within the distinct subgroups. E-boxes were found in most promoters and were usually of the E2A type. A mouse kappa promoter was studied functionally. Two elements were identified 5' of the octamer, the pd and the k-Y element. Both had weak stimulatory activity per se, but interacted with the octamer and each other to direct high levels of transcription. The two ets proteins PU.1 and elf-1 were shown to bind to the k-Y element. Two independent protein binding sites were found in the pd element, and both were needed for function of the element. One of the pd interacting proteins was identified as CArG box binding factor-A (CBF-A) after purification and amino acid sequencing. The protein interacted with both single- and double-stranded DNA, and interacted with elf-1 and PU.1 in pull down assays. A novel k-Y binding protein, Spi-C, was identified in an yeast one-hybrid screen. The protein was closely related to PU.1 within the ets domain but not outside of it. Spi-C was highly expressed in peripheral B cells while neither in pre-B cell lines nor plasmacytomas. No expression was found in a panel of different cell lines and tissues that did not represent B cells, except for weak expression in a macrophage cell line.