The IL-1 alpha and beta genes are closely linked (less than 70 kb) on mouse chromosome 2.

The murine IL-1 alpha and IL-1 beta genes encode structurally and evolutionarily related cytokines that exert a regulatory role in numerous physiological processes including hemopoiesis. Previous studies have shown these genes to be closely linked in the F region of mouse chromosome 2. Here we show, using pulsed-field gel electrophoresis, that the IL-1 alpha and beta genes of the CBA/H mouse are very closely linked and contained within a SmaI genomic fragment of approximately 70 kb. From conventional and PFGE analyses we suggest that IL-1 beta lies 5' to IL-1 alpha and that the two genes are in the same orientation and separated by approximately 50 kb. The apparent clustering of such hemopoietic genes is discussed in relation to evolutionary tandem gene duplication and possible associations with chromosomal fragile sites and leukemogenesis.