Laboratory of Metabolic Diseases and Aging, INDICyO Program, Institut Pasteur de Montevideo, Montevideo, Uruguay.
Departamento de Fisiología, Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.
Sci Rep. 2019 Oct 7;9(1):14381. doi: 10.1038/s41598-019-50789-7.
The protein Deleted in Breast Cancer-1 is a regulator of several transcription factors and epigenetic regulators, including HDAC3, Rev-erb-alpha, PARP1 and SIRT1. It is well known that DBC1 regulates its targets, including SIRT1, by protein-protein interaction. However, little is known about how DBC1 biological activity is regulated. In this work, we show that in quiescent cells DBC1 is proteolytically cleaved, producing a protein (DN-DBC1) that misses the S1-like domain and no longer binds to SIRT1. DN-DBC1 is also found in vivo in mouse and human tissues. Interestingly, DN-DBC1 is cleared once quiescent cells re-enter to the cell cycle. Using a model of liver regeneration after partial hepatectomy, we found that DN-DBC1 is down-regulated in vivo during regeneration. In fact, WT mice show a decrease in SIRT1 activity during liver regeneration, coincidentally with DN-DBC1 downregulation and the appearance of full length DBC1. This effect on SIRT1 activity was not observed in DBC1 KO mice. Finally, we found that DBC1 KO mice have altered cell cycle progression and liver regeneration after partial hepatectomy, suggesting that DBC1/DN-DBC1 transitions play a role in normal cell cycle progression in vivo after cells leave quiescence. We propose that quiescent cells express DN-DBC1, which either replaces or coexist with the full-length protein, and that restoring of DBC1 is required for normal cell cycle progression in vitro and in vivo. Our results describe for the first time in vivo a naturally occurring form of DBC1, which does not bind SIRT1 and is dynamically regulated, thus contributing to redefine the knowledge about its function.
乳腺癌缺失蛋白 1 是几种转录因子和表观遗传调节剂的调节剂，包括 HDAC3、Rev-erb-α、PARP1 和 SIRT1。众所周知，DBC1 通过蛋白-蛋白相互作用调节其靶标，包括 SIRT1。然而，关于 DBC1 生物活性如何调节的信息知之甚少。在这项工作中，我们表明在静止细胞中，DBC1 被蛋白水解切割，产生一种缺失 S1 样结构域且不再与 SIRT1 结合的蛋白质（DN-DBC1）。DN-DBC1 在体内也存在于小鼠和人类组织中。有趣的是，DN-DBC1 在静止细胞重新进入细胞周期后被清除。使用部分肝切除后的肝再生模型，我们发现 DN-DBC1 在体内再生过程中下调。事实上，WT 小鼠在肝再生过程中显示 SIRT1 活性下降，与 DN-DBC1 下调和全长 DBC1 的出现巧合。在 DBC1 KO 小鼠中未观察到对 SIRT1 活性的这种影响。最后，我们发现 DBC1 KO 小鼠在部分肝切除后细胞周期进程和肝再生发生改变，表明 DBC1/DN-DBC1 转变在体内细胞离开静止后正常细胞周期进程中起作用。我们提出，静止细胞表达 DN-DBC1，其要么取代全长蛋白，要么与全长蛋白共存，并且在体外和体内恢复 DBC1 是正常细胞周期进程所必需的。我们的结果首次在体内描述了一种自然存在的 DBC1 形式，其不与 SIRT1 结合且动态调节，从而有助于重新定义其功能知识。
