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  • Title: A novel enhancer element in the human IL-4 promoter is suppressed by a position-independent silencer.
    Author: Li-Weber M, Krafft H, Krammer PH.
    Journal: J Immunol; 1993 Aug 01; 151(3):1371-82. PubMed ID: 8393045.
    Abstract:
    IL-4 is a pleiotropic cytokine that regulates T cell-dependent immune responses. We identified and characterized a novel enhancer, positive regulatory element I (PRE-I), in the 5' region of the promoter of the human IL-4 gene. The functional core element of PRE-I is -239GTGTAATTTCCTATGC-224. Two novel nuclear proteins, POS-1 and POS-2, were found to specifically bind to the core element and function as transcriptional activators. The function of PRE-I did not require T cell stimulation and was not restricted to T cells. However, mutations in the core element of PRE-I significantly reduced the promoter activity and completely impaired inducibility of the promoter. In the human IL-4 promoter the enhancer function of PRE-I is strongly suppressed. A negative regulatory element (NRE), 45 bp upstream of PRE-I, directly represses PRE-I enhancer activity. Repression of PRE-I by NRE does not require a particular order or arrangement of positive and negative regulatory sequences. The IL-4 NRE may also down-regulate other enhancers, such as the murine sarcoma virus and the SV40 enhancers. Thus, the IL-4 NRE may represent a new type of cis regulatory element that carries the properties of a silencer but down-regulates enhancer instead of basal promoter activity.
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