Bisotto S, Minorgan S, Rehfuss R P
Laboratory of Molecular Endocrinology, Royal Victoria Hospital, McGill University, Montreal, Quebec, Canada H3A 1A1.
J Biol Chem. 1996 Jul 26;271(30):17746-50. doi: 10.1074/jbc.271.30.17746.
The CREB-binding protein (CBP) plays a central role in the regulation of gene expression by several different second messenger pathways including serum growth factors, cAMP and phorbol esters. CBP specifically binds to the phosphorylated forms of CREB and c-Jun and is thought to activate transcription through a C-terminal activation domain. In this report, we demonstrate that the C terminus of CBP is dispensable for its ability to stimulate phospho-CREB activity, and, further, that the deletion of this domain produces highly active, mutant forms of CBP. The novel N-terminal activation identified by this deletional analysis consists of the first 714 amino acids of CBP and is sufficient for high levels of transcriptional activity. This domain is also capable of stimulating the activity of a second cAMP-regulated factor, ATF-1. Surprisingly, ATF-1 activity is not significantly stimulated by full-length CBP suggesting that the C-terminal domain of CBP may also serve to regulate ATF-1/CBP activity. Additionally, the demonstration that one of our hyperactive CBP mutants is able to activate a nonphosphorylatable mutant of CREB (M1 CREB) provides the first evidence that CBP may play a role in regulating the basal transcriptional activity of CREB.
CREB结合蛋白（CBP）在通过多种不同的第二信使途径（包括血清生长因子、cAMP和佛波酯）调控基因表达中发挥核心作用。CBP特异性结合CREB和c-Jun的磷酸化形式，并被认为通过C端激活域激活转录。在本报告中，我们证明CBP的C端对于其刺激磷酸化CREB活性的能力并非必需，而且，进一步地，该结构域的缺失产生了高活性的CBP突变形式。通过这种缺失分析鉴定出的新型N端激活域由CBP的前714个氨基酸组成，足以实现高水平的转录活性。该结构域还能够刺激第二种cAMP调节因子ATF-1的活性。令人惊讶的是，全长CBP并未显著刺激ATF-1的活性，这表明CBP的C端结构域也可能用于调节ATF-1/CBP的活性。此外，我们的一个高活性CBP突变体能够激活CREB的非磷酸化突变体（M1 CREB），这一证明首次提供了CBP可能在调节CREB的基础转录活性中发挥作用的证据。
