Sci. STKE, 20 March 2001
Transcription An IB Sink
The transcription factor NF-B has critical functions in control of immune and inflammatory responses (see STKE Review by Rothwarf and Karin). The required strict control of NF-B transcriptional activity is mediated in part by inhibitory IB proteins. When the IB proteins are degraded, NF-B activity is increased. IB proteins appear to act in multiple ways to hold NF-B activity in check. When it interacts with NF-B, IBα appears to hide the nuclear localization sequence of the NF-B Rel subunit and also to inhibit DNA binding by NF-B. IBα also moves between the cytoplasm and nucleus through the actions of a nuclear localization sequence and a nuclear export sequence that interacts with the importin protein CRM1. Such nuclear export may also carry NF-B-IB complexes out of the nucleus and contribute to transcriptional control. Tam and Sen now report that the regulatory properties appear to differ in various IB family members. In particular, they show that IBβ and IB do not shuttle out of the nucleus by CRM1-dependent transport. The authors suggest that, rather than facilitating nuclear export of NF-B, IBβ and IB function primarily by sequestration of NF-B in the cytoplasm.
Citation: An IB Sink. Sci. STKE 2001, tw5 (2001).
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