Düvel K, Broach J R
Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
Curr Top Microbiol Immunol. 2004;279:19-38. doi: 10.1007/978-3-642-18930-2_2.
The TOR pathway controls cellular functions necessary for cell growth and proliferation of yeast and larger eukaryotes. The search for members of the TOR signaling cascade in yeast led to the discovery of type 2A protein phosphatases (PP2A) as important players within the pathway. We describe the roles in yeast of PP2A and the closely related phosphatase, Sit4, and then focus on complexes formed between the catalytic subunit of these phosphatases and Tap42, a direct target of the Tor protein kinases in yeast. Recent results suggest that Tap42 mediates many of the Tor functions in yeast, especially those involved in transcriptional modulation. However, whether Tap42 executes its function by inhibiting phosphatase activity or by activating phosphatases is still uncertain. In addition, Tor affects some transcriptional and physiological processes through Tap42 independent pathways. Thus, Tor proteins use multiple mechanisms to regulate transcriptional and physiological processes in yeast.
TOR信号通路控制酵母及其他较大真核生物细胞生长和增殖所必需的细胞功能。对酵母中TOR信号级联成员的研究发现，2A型蛋白磷酸酶（PP2A）是该信号通路中的重要参与者。我们描述了PP2A以及与之密切相关的磷酸酶Sit4在酵母中的作用，然后重点关注这些磷酸酶的催化亚基与Tap42（酵母中Tor蛋白激酶的直接靶点）形成的复合物。最近的研究结果表明，Tap42介导了酵母中许多Tor的功能，尤其是那些参与转录调控的功能。然而，Tap42是通过抑制磷酸酶活性还是激活磷酸酶来执行其功能仍不确定。此外，Tor通过不依赖Tap42的途径影响一些转录和生理过程。因此，Tor蛋白利用多种机制来调节酵母中的转录和生理过程。
