1996 Fiscal Year Final Research Report Summary

Switch mechanism between mitotic growth and cell differentiation

Research Project

Project/Area Number	07457028
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Research Field	General medical chemistry
Research Institution	The University of Tokyo
Principal Investigator	NAGATA Akihisa The University of Tokyo, Faculty of Medicine, Lecrturer, 医学部, 講師 (50155933)
Co-Investigator(Kenkyū-buntansha)	MURAKAMI Hiroshi The University of Tokyo, Faculty of Medicine, Research Associate, 医学部, 助手 (80262020) JINNO Shigeki The University of Tokyo, Faculty of Medicine, Research Associate, 医学部, 助手 (10251224) OKAYAMA Hiroto The University of Tokyo, Faculty of Medicine, Professor, 医学部, 教授 (40111950)
Project Period (FY)	1995 – 1996
Keywords	pat1 / G1 phase / Rod1 / rsv1 / nrd1 / cell differentiation / Igs69
Research Abstract	In the fission yeast S.Pombe, switching from mitotic growth to sexual development is regulated by a highly complex mechanism. To isolate new genes involved in this switch mechanism, we have searched for multicopy suppressors of a patl-114^<ts> mutant, and identified three genes named rvs1^+, Igs69^+ and nrd1^+. rsv1 (Required for Stationary phase Viability) is essential for fission yeast cell viability in a stationary induced by glucose starvation. rsv1^+ encodes a 47kD protein with two zinc finger motifs that show limitid homology with the Aspergillus Nidulans CREA,the budding yeast MIG1 and the mammalian Egr-1/NGF1-A genes. Cells deleted for rsv1^+ are unable to survive glucose starvation. Transcription of rsv1 is negatively regulated by the cAMP pathway and induced during glucose starvation. Viavility loss of the cells with the constitutively activated cAMP during entry into stationary phase is largely attributavle to poor induction of rsv1^+. Analysis also shows that cells need to r … More eceive starvation signals before entry into the stationary phase in order to maintain viavility in a glucose poor environment. Igs69^+ encodes a 70kD protein with two zinc finger motifs like rsv1^+. Cells deleted for Igs69^+ are viable but grow slowly. It may be trouble with the cell separation. nrd1^+ encodes a 52kD protein with four repeats of the RNA binding motif composed of two highly conserved amino acid sequences, RNP1 and RNP2. Cells deleted for nrd1^+ are viable and grow at a normal growth rate, but are markedly enhanced in conjugation in the presence of a plenty of nitrogen. Overexpression of nrd1^+ inhibits mating. In a close correlation with enhancement of mating, in ned1^+ cells, the basal level of ste11^+ expression is markedly elevated. nrd1^+ mRNA diminishes during nitrogen stavation. nrd1^+ rescues patl-114 cyc17^- double mutants. Conversely, res1^+, cyc17^+ or pka1^+ can rescue patl-114 nrd1^- cells. Thus, nrd1^+ is a key negative regulator of sexual differentiation, and its principal function is likely to be repression of ste11^+. Moreover, we have isolated Rod1 gene, a rat homolog of fission yeast nrd1^+. Rod1 encodes a 57kD protein with with four repeats of the RNA binding motif cpmposed of two highly conserved amino acid sequences, RNP1 and RNP2 like nrd^+. Rodl can substitute for nrd1^+ in S.pombe cell. This suggest that the differentiation regulatory mechanism is conserved evolutionarily. Less