Functions of Myc and c-Myc-binding proteins

1).一条新的c-Myc转录抑制途径及其靶基因的鉴定我们发现MM-1与转录辅阻遏子TIF13结合，并且MM-1向c-Myc募集了包括HDAC1和mSin3在内的辅阻遏子复合体，从而抑制了c-Myc的转录活性。为了确定这一途径的靶基因，首先建立了一个携带显性-阴性TIFI型β的MycER细胞系，其中辅阻遏子复合体不被招募到c-Myc。然后应用DNA微阵列方法鉴定与MycER细胞相比在该系中表达上调的基因。利用该系统，我们鉴定c-fms癌基因为c-Myc-MM-1抑制基因。发现第三个E-box存在的mc-FINS启动子必须被c-Myc2抑制。我们还鉴定了Elongin B、26S蛋白酶体亚单位Rpt3和Rpn12为MM-1相关蛋白。由于这些蛋白质对UB…起作用随着蛋白质的进一步降解，我们进一步验证了MM-1在c-Myc降解中发挥作用的可能性。结果表明，MM-1是通过一种新的E3泛素连接酶复合体Spk2、cullin 1、Elongon B来促进c-Myc的降解。这些结果表明MM-1是负调控c-Myc功能的关键蛋白，突变使MM-1的这些功能丧失会导致c-Myc的肿瘤形成。3)AMY-1与几种PKA锚定蛋白的蛋白激酶A(P1(A)调节亚基2(RII)结合结构域，包括AKAP149、S-AKAP84和AKAP95，根据相关的AKAP，AMY-1也定位在高尔基体中，定位于细胞质或细胞核。AMY-1与BIG2和BIG1抑制的鸟嘌呤核苷酸交换蛋白BIG2和BIG1的第一个RII结合域结合，并且即使在抑制BIG2的鸟核苷酸交换活性的BIG2存在的情况下也与BIG2共定位。AMY-1也被发现定位于跨高尔基体。这些结果表明，AMY-1作为辅因子在BIG2或BIG1的鸟嘌呤核苷酸交换反应中起作用。较少

1).Identification of a novel transrepression pathway of c-Myc and its target geneWe have found that MM-1 bound to TIF13, a transcriptional corepressor, and that MM-1 recruited a corepressor complex, including HDAC1 and mSin3, to c-Myc, thereby leading to repressing c-Myc transcription activity. To identify target genes to this pathway, a MycER cell line harboring a dominant-negative form of TIFiβ, in which the corepressor complex was not recruited to c-Myc, was first established. DNA-microarray method was then applied to identify genes whose expressions were upregulated in this line compared to those in MycER cells. By this system we identified c-fms oncogene as the c-Myc-MM-1 repressed gene. It was then found that third E-box present m c-fins promoter was essential to be repressed by c-Myc.2). Identification of a novel degradation pathway of c-Myc.We have also identified Elongin B, 26Sproteasome subunits Rpt3 and Rpn12 as MM-1-associated proteins. Since these proteins functions for ub … More iquitination and degradation of proteins, we then tested a possibility that MM-1 plays a role in c-Myc degradation. The results indicate that MM-1 stimulated c-Myc degradation through the novel E3 ubiquitin ligase complex, including Spk2, Cullin 1, Elongon BThese findings indicate that MM-1 is a key protein that negatively regulates c-Myc function and that lost of these functions of MM-1 by mutations leads to tumor formation by c-Myc.3) AMY-1 was found to bind to the protein kinase A (P1(A) regulatory subunit type 2 (RII)-binding domains of several PKA-anchoring proteins, AKAPs, including AKAP149, S-AKAP84 and AKAP95, and to be localized in the cytoplasm or nuclei depending on associated AKAPs AMY-1 was also localized in the Golgi apparatus. AMY-1 bound to the first RII-binding domains of the brefeldin A-inhibited guanine nucleotide-exchange proteins BIG2 and BIG1 and colocalized with BIG2 even in the presence of brefeldin A, which inhibits guanine nucleotide-exchange activity of BIG2. AMY-1 was also found to be localized in the trans-Golgi apparatus. These results suggest that AMY-1 as a cofactor plays a role in guanine nucleotide-exchange reaction of BIG2 or BIG1. Less