類固醇轉錄因子SF-1對中心體複製調控機制之研究

Abstract

DNA損傷監控蛋白 (DNA damage checkpoint protein) 表現在細胞核以及中心體。這些損傷監控蛋白在細胞核中負責維持基因組的完整性；但是他們在中心體的功能卻仍不清楚。在本篇研究中發現，有一種稱之為DNA-PK的損傷監控蛋白不僅存在於中心體，而且還負責調控中心體的複製。在腎上腺皮質癌細胞中，DNA-PK的活性是受到SF-1 (NR5A1)所抑制。SF-1透過與DNA-PK的次單元Ku70/80結合，使得Ku70/80無法與DNA-PK的催化單元(DNA-PKcs)結合，進而抑制DNA-PK的活化。 當SF-1的表現被shRNA所抑制時，會導致中心體內的DNA-PK異常活化，進而活化其下游的Akt訊息傳導路徑。被活化的Akt訊息傳導路徑會導致

DNA damage checkpoint proteins reside in the nucleus and the centrosome. In the nucleus, they maintain genomic integrity; however, their function in the centrosome remains unclear. Here I show that one such checkpoint protein, DNA-PK, controls centrosome duplication. In adrenocortical Y1 cells, DNA-PK activity is inhibited by SF-1 (NR5A1), which interacts with and sequesters Ku70/Ku80 from DNA-PK catalytic subunit in the centrosome. Following SF-1 depletion by shRNA, centrosomal DNA-PK was aberrantly activated, triggering centrosomal Akt (PKB) signaling, leading to accumulation of β-catenin and Cyclin A/CDK2 in the centrosome, causing centriole splitting and over-duplication. SF-1 depletion did not, however, induce DNA damage response and Akt signaling in other cellular compartments. Inhibition of DNA-PK/Akt in HeLa, U2OS, and H1299 cells also blocked centrosome over-duplication upon replication stress. I have, thus, uncovered a novel function of DNA-PK/Akt signaling in controlling centrosome duplication.