H2O2에 의한 Hog1 활성에서 Swi6의 역할 규명

Abstract

Saccharomyces cerevisiae는 주위 환경변화에 적응하여 살아가야 위해, 세포 내 신호전달 체계를 발전시켜왔다. 환경변화에 적응하기 위한 다양한 세포신호전달 체계 중, Mitogen-Activated Protein Kinase (MAPK) 과정이 가장 잘 알려져 있다. S. cerevisiae에는 5가지의 MAPK가 있는데, 본 연구에서는 HOG (High Osmolarity Glycerol)와 CWI (Cell Wall Integrity) pathway에 초점을 맞췄다. Hydrogen peroxide (H2O2)는 대표적인 ROS (Reactive Oxygen Species)로서 본 연구에서 다룬 중점적인 외부 스트레스 요인이다. H2O2에 의하여 HOG pathway의 Hog1 MAPK와 CWI pathway의 Stl2 MAPK가 활성화 되고, CWI pathway의 downstream 전사인자인 Swi6가 없을 시 Hog1이 활성화가 되지 않음이 밝혀졌다. SWI6 유전자의 Cys-354, Cys-380, Ser-160가 Hog1 활성에 중요한 역할을 한다. 또한 Hog1과 Swi6는 G1 phase cell-cycle progression에도 관여한다. H2O2에 의하여 G1 phase cell-cycle arrest가 일어난다는 것을 확인하였고, HOG1이 과 발현 되었을 시 더 강한 G1 phase cell-cycle arrest가 일어난다. SWI6 유전자 자체의 결손이 G1 phase cell-cycle arrest를 유발하고, H2O2에 의하여 cell-cycle arrest가 더 지속됨이 밝혀졌다. 어떻게 SWI6의 Cys-354, Cys-380, Ser-160 잔기들이 Hog1과 상호작용을 하고, cell-cycle 측면에서 Swi6와 Hog1의 관계를 위한 연구가 더 필요하다.;Saccharomyces cerevisiae cells have developed complex mechanisms to survive various environmental insults. Two mitogen-activated protein kinase (MAPK) pathways, i.e., high osmolarity glycerol (HOG) and cell wall integrity (CWI) pathways, play important roles in adapting to most of environmental insults specific environmental stress. It has been known that the MAPKs Hog1 and Slt2 are activated by hydrogen peroxide (H2O2), which is a typical reactive oxygen species (ROS). Particularly, it remains obscure how the two pathways interplay in response to H2O2. As an initial step to understand it, the effect of SWI6 on Hog1 activation, which encodes a CWI pathway downstream transcription factor and cell cycle regulator, was investigated: Hog1 activation byH2O2 occurs little in the absence of Swi6. Further point mutation analysis revealed three amino acid residues (Cys354, Cys380 and Ser160) that are required for Hog1 activation. As both Hog1 and Swi6 are important cell-cycle progression regulators under stress conditions, it was examined whether the cell-cycle progression was affected by the presence of H2O2. Impact of H2O2 on cell-cycle progression: the cell cycle was severe delayed with being attested at G1. This observation is contrary to the previously reported G2 arrest (Flattery-O’Brien and Dawes, 1998, J Biol Chem 273: 68564-8571). In the presence of H2O2 deletion of SWI6 delayed the cell cycle to an extent comparable to what deletion of HOG1 did, suggesting that HOG1 and SWI6 are closely associated in the cell-cycle progression. This study shows for the first time that Swi6 is required for Hog1 activation in response to H2O2, although detailed mechanisms is not defined.