Multiple chromatin-bound protein kinases assemble factors that regulate insulin gene transcription

During the onset of diabetes, pancreatic β cells become unable to produce sufficient insulin to maintain blood glucose within the normal range. Proinflammatory cytokines have been implicated in impaired β cell function. To understand more about the molecular events that reduce insulin gene transcription, we examined the effects of hyperglycemia alone and together with the proinflammatory cytokine interleukin-1β (IL-1β) on signal transduction pathways that regulate insulin gene transcription. Exposure to IL-1β in fasting glucose activated multiple protein kinases that associate with the insulin gene promoter and transiently increased insulin gene transcription in β cells. In contrast, cells exposed to hyperglycemic conditions were sensitized to the inhibitory actions of IL-1β. Under these conditions, IL-1β caused the association of the same protein kinases, but a different combination of transcription factors with the insulin gene promoter and began to reduce transcription within 2 h; stimulatory factors were lost, RNA polymerase II was lost, and inhibitory factors were bound to the promoter in a kinase-dependent manner.