RMIL-6 STIMULATES THE TRANSCRIPTIONAL ACTIVITY OF THE RAT PF4 GENE

We have examined the effect of recombinant murine interleukin-6 (rmIL- 6) on megakaryocytopoiesis in a liquid rat bone marrow culture system. At concentrations of IL-6 up to 100 ng/mL, no stimulation of megakary ocyte ploidy was observed. However, transient expression studies revea led that IL-6 did have a significant effect on the transcriptional act ivity of the platelet factor four (PF4) gene, a platelet alpha-granule protein gene uniquely expressed in megakaryocytes. Furthermore, when the amount of PF4 message was directly measured in megakaryocytes, it was increased three-fold in response to IL-6. We also note that the PF 4 promoter contains a hexamer, CTGGGA, described as the IL-6-responsiv e element in other genes. Our results suggest that the platelet progen y of IL-6-stimulated megakaryocytes may have altered alpha-granule con stituents.