Griffioen G, Anghileri P, Imre E, Baroni M D, Ruis H
Vienna Biocenter, Institut für Biochemie und Molekulare Zellbiologie der Universität Wien and Ludwig Boltzmann-Forschungstelle für Biochemie, Dr. Bohrgasse 9, A-1030 Wien, Austria.
J Biol Chem. 2000 Jan 14;275(2):1449-56. doi: 10.1074/jbc.275.2.1449.
In budding yeast, cAMP-dependent protein kinase (PKA) plays a central role in the nutritional control of metabolism, cell cycle, and transcription. This study shows that both the regulatory subunit Bcy1p and the catalytic subunit Tpk1p associated with it are predominantly localized in the nucleus of rapidly growing cells. Activation of nuclear PKA by cAMP leads to fast entry of a significant part of Tpk1p into the cytoplasm, while the regulatory subunit remains nuclear. In contrast to rapidly proliferating cells, both Bcy1p and Tpk1p are distributed over nucleus and cytoplasm in cells growing on a nonfermentable carbon source or in stationary phase cells. These results demonstrate that at least two different mechanisms determine the subcellular localization of PKA; cAMP controls the localization of Tpk1p, and the carbon source determines that of Bcy1p. The N-terminal domain of Bcy1p serves to target it properly during logarithmic and stationary phase. Studies with Bcy1p mutant versions unable to concentrate in the nucleus revealed that cells producing them are less viable in stationary phase than wild type cells, display delayed reproliferation following transfer to fresh growth medium, and, as diploids, exhibit reduced efficiency of sporulation.
在芽殖酵母中，环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）在新陈代谢、细胞周期和转录的营养控制中发挥核心作用。本研究表明，调节亚基Bcy1p及其相关的催化亚基Tpk1p主要定位于快速生长细胞的细胞核中。cAMP激活细胞核中的PKA会导致相当一部分Tpk1p快速进入细胞质，而调节亚基仍保留在细胞核中。与快速增殖的细胞不同，在以不可发酵碳源生长的细胞或静止期细胞中，Bcy1p和Tpk1p均分布于细胞核和细胞质中。这些结果表明，至少有两种不同机制决定PKA的亚细胞定位；cAMP控制Tpk1p的定位，而碳源决定Bcy1p的定位。Bcy1p的N端结构域有助于其在对数期和静止期正确定位。对无法在细胞核中聚集的Bcy1p突变体进行的研究表明，产生这些突变体的细胞在静止期的活力低于野生型细胞，转移到新鲜生长培养基后再增殖延迟，并且作为二倍体，其孢子形成效率降低。
