Snf1 promotes phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 by activating Gcn2 and inhibiting phosphatases Glc7 and Sit4.
Snf1 is the ortholog of mammalian AMP-activated kinase and is responsible for activation of glucose-repressed genes at low glucose levels in budding yeast. We show that Snf1 promotes the formation of phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha-P), a regulator of general and gene-specific translation, by stimulating the function of eIF2alpha kinase Gcn2 during histidine starvation of glucose-grown cells. Thus, eliminating Snf1 or mutating its activation loop lowers Gcn2 kinase activity, reducing the autophosphorylation of Thr-882 in the Gcn2 activation loop, and decreases eIF2alpha-P levels in starved cells. Consistently, eliminating Reg1, a negative regulator of Snf1, provokes Snf1-dependent hyperphosphorylation of both Thr-882 and eIF2alpha. Interestingly, Snf1 also promotes eIF2alpha phosphorylation in the nonpreferred carbon source galactose, but this occurs by inhibition of protein phosphatase 1alpha (PP1alpha; Glc7) and the PP2A-like enzyme Sit4, rather than activation of Gcn2. Both Glc7 and Sit4 physically interact with eIF2alpha in cell extracts, supporting their direct roles as eIF2alpha phosphatases. Our results show that Snf1 modulates the level of eIF2alpha phosphorylation by different mechanisms, depending on the kind of nutrient deprivation existing in cells.
Cherkasova
Vera
V
Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892, USA.
Qiu
Hongfang
H
Hinnebusch
Alan G
AG
D003470:Culture Media / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism*; D005690:Galactose / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D006639:Histidine / Q000172:deficiency / Q000494:pharmacology; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D021122:Protein Subunits / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*
D003470:Culture Media; D015852:Eukaryotic Initiation Factor-2; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D006639:Histidine; C071570:SNF1-related protein kinases; C512912:GCN2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; C092048:GLC7 protein, S cerevisiae; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; C104343:SIT4 protein, S cerevisiae; D005947:Glucose; D005690:Galactose
Front Biosci. 2008 Jan 01;13:2408-20
17981722
Mol Cell Biol. 2005 Dec;25(23):10566-79
16287868
J Biol Chem. 2001 Sep 28;276(39):36460-6
11486005
Cell. 1986 Apr 25;45(2):201-7
3516411
Proc Natl Acad Sci U S A. 1983 Sep;80(17):5374-8
6351059
Mol Cell Biol. 1992 Dec;12(12):5700-10
1333044
Mol Cell Biol. 1998 Apr;18(4):2282-97
9528799
Yeast. 2008 Oct;25(10):745-54
18949820
Genetics. 1987 Aug;116(4):541-5
3305158
Proc Natl Acad Sci U S A. 2003 Jul 22;100(15):8839-43
12847291
J Biol Chem. 2005 Aug 12;280(32):29289-99
15964839
J Biol Chem. 2009 Sep 11;284(37):25254-67
19546227
Genes Dev. 2002 May 15;16(10):1271-80
12023305
Mol Cell Biol. 2004 Mar;24(6):2560-72
14993292
Curr Biol. 2003 Aug 5;13(15):1299-305
12906789
Mol Cell Biol. 1998 Nov;18(11):6273-80
9774644
Proc Natl Acad Sci U S A. 1998 May 26;95(11):6245-50
9600950
Eukaryot Cell. 2006 Nov;5(11):1831-7
16980405
FEBS Lett. 2005 Jan 17;579(2):512-6
15642368
Genes Dev. 2003 Apr 1;17(7):859-72
12654728
J Biol Chem. 2008 Dec 19;283(51):35889-98
18955495
J Biol Chem. 2008 Mar 14;283(11):7064-73
18195013
Int J Biochem Cell Biol. 2006;38(9):1476-81
16647875
Curr Biol. 1996 Nov 1;6(11):1426-34
8939604
Annu Rev Microbiol. 2005;59:407-50
16153175
Mol Cell Biol. 2009 Mar;29(6):1592-607
19114556
J Biol Chem. 2002 Aug 23;277(34):30675-83
12070158
Proc Natl Acad Sci U S A. 2004 Aug 3;101(31):11269-74
15277680
Mol Cell Biol. 2000 Apr;20(8):2706-17
10733573
Mol Cell. 2000 Nov;6(5):1099-108
11106749
Cell. 1992 Feb 7;68(3):585-96
1739968
Mol Cell Biol. 1995 Aug;15(8):4497-506
7623840
J Biol Chem. 2007 Jun 8;282(23):16838-45
17438333
Mol Cell Biol. 1990 Jun;10(6):2820-31
2188100