Schizosaccharomyces pombe gad7+ encodes a phosphoprotein with a bZIP domain, which is required for proper G1 arrest and gene expression under nitrogen starvation.
BACKGROUND
Fission yeast cells arrest at G1 phase when starved of nitrogen. The molecular mechanism that ensures this arrest is poorly understood. We took a genetic approach to this problem.


RESULTS
The fission yeast gad7-1 mutant failed to arrest at G1 when starved of nitrogen, and was poor in mating and sporulation. The gad7 gene was cloned by complementation. The deduced gad7 gene product was a bZIP protein of 566 amino acids, which could bind to the CRE (cAMP response element) sequence in vitro. Disruption of gad7 resulted in the same phenotypes as gad7-1. Expression of ste11, which encodes a key transcription factor for sexual development, was not inducible in the disruptant. Gad7 was co-immunoprecipitated with another bZIP protein Pcr1, suggesting that the two proteins form a heterodimer in vivo. Gad7 was phosphorylated, and the state of its phosphorylation appeared to be modified in pka1delta or wis1delta cells.


CONCLUSIONS
Gad7, a CRE-binding protein that cooperates with Pcr1, is required for proper G1 arrest and gene expression under nitrogen starvation. Gad7 is a phosphoprotein, whose activity may be regulated by protein kinases including the cAMP-dependent protein kinase (Pka1) and Wis1 osmosensory MAP kinase kinase.
Kanoh
J
J
Department of Biophysics and Biochemistry, School of Science, University of Tokyo, Hongo, Japan.
Watanabe
Y
Y
Ohsugi
M
M
Iino
Y
Y
Yamamoto
M
M
D051697:Activating Transcription Factor 1; D000595:Amino Acid Sequence; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins / Q000235:genetics; D003001:Cloning, Molecular; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics; D004271:DNA, Fungal / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics*; D051790:G-Box Binding Factors; D016193:G1 Phase / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D015698:Genomic Library; D047908:Intracellular Signaling Peptides and Proteins; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009584:Nitrogen; D010750:Phosphoproteins; D010766:Phosphorylation; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D011993:Recombinant Fusion Proteins; D015183:Restriction Mapping; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins; D017422:Sequence Analysis, DNA; D014157:Transcription Factors / Q000235:genetics*
D051697:Activating Transcription Factor 1; D050976:Basic-Leucine Zipper Transcription Factors; D002352:Carrier Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D051790:G-Box Binding Factors; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; D014157:Transcription Factors; C106740:atf1 protein, S pombe; C015482:protein kinase modulator; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C072068:wis1 protein, S pombe; D009584:Nitrogen