| Co-Investigator(Kenkyū-buntansha) |
ARIGA Sanae Hokkaido Univ., Grad.School of Aggr., Prof., 大学院・農学研究科, 教授 (90184283)
KITAURA Hirotake Hokkaido Univ., Grad.School of Pharm.Sci., Instruc., 大学院・薬学研究科, 助手 (10281817)
TAIRA Takahiro Hokkaido Univ., Grad.School of Pharm.Sci., Asso.Prof., 大学院・薬学研究科, 助教授 (70197036)
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| Research Abstract |
1).Identification of a novel transrepression pathway of c-Myc and its target gene
We 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
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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 B
These 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
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