Pearson K L, Hunter T, Janknecht R
Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN 55905, USA.
Biochim Biophys Acta. 1999 Dec 23;1489(2-3):354-64. doi: 10.1016/s0167-4781(99)00166-9.
Smad1 is the intracellular effector of bone morphogenetic proteins (BMPs), a growth factor family well known to stimulate bone and cartilage formation. Smad1 becomes phosphorylated by the cognate BMP transmembrane receptor protein kinases, associates with the common mediator Smad4 and translocates to the nucleus where it is involved in regulation of gene transcription. In this report we demonstrate that Smad1 interacts with the paralogous coactivators p300 and CBP both in vitro and in vivo. The N- and C-termini of Smad1 negatively interfere with binding to p300/CBP, and the C-terminal half of Smad1 harbors two interaction domains both binding to the same region near the C-terminus of p300/CBP. We show that Smad1 as well as a Gal4 fusion with the C-terminal half of Smad1 stimulate gene transcription in a cooperative fashion with p300/CBP. Phosphorylation of Smad1 enhances its binding to CBP and thereby further stimulates Smad1-dependent transcription. These results provide a mechanism how phosphorylated Smad1 regulates gene activity by interaction with p300/CBP, and factors associated with these bridging coactivators.
Smad1是骨形态发生蛋白（BMPs）的细胞内效应因子，骨形态发生蛋白是一个众所周知的能够刺激骨和软骨形成的生长因子家族。Smad1被同源的BMP跨膜受体蛋白激酶磷酸化，与共同介质Smad4结合并转运至细胞核，在细胞核中参与基因转录的调控。在本报告中，我们证明Smad1在体外和体内均与同源共激活因子p300和CBP相互作用。Smad1的N端和C端对与p300/CBP的结合具有负向干扰作用，并且Smad1的C端一半含有两个相互作用结构域，这两个结构域均与p300/CBP C端附近的同一区域结合。我们表明，Smad1以及与Smad1 C端一半融合的Gal4以与p300/CBP协同的方式刺激基因转录。Smad1的磷酸化增强了其与CBP的结合，从而进一步刺激依赖Smad1的转录。这些结果提供了一种机制，即磷酸化的Smad1如何通过与p300/CBP以及与这些桥梁共激活因子相关的因子相互作用来调节基因活性。
