title: D-type cyclin expression is decreased and p21 and p27 CDK inhibitor expression is increased when tsBN462 CCG1/TAFII250 mutant cells arrest in G1 at the restrictive temperature.
abstract: BACKGROUND
  The tsBN462 temperature-sensitive mutant hamster cell line exhibits cell cycle arrest and apoptosis at the restrictive temperature of 39.5 degrees C, due to a point mutation in the CCG1/TAFII250 gene, which encodes a component of the general transcription factor TFIID.
  
  
  RESULTS
  We now report that CCG1/TAFII250 persisted as a complex with TBP and associated proteins (TAFs) in tsBN462 cells at the restrictive temperature. FACScan analysis revealed that the tsBN462 mutation resulted in a failure to progress out of G0 into G1. Using two-dimensional gel electrophoresis we observed a decrease in the synthesis of several proteins, starting in the middle of the G1 phase, becoming very pronounced during late G1. The expression of the immediate early genes c-fos, c-jun and c-myc was normally induced by serum treatment of quiescent cells at the restrictive temperature, whereas expression of cyclins A, D1 and D3 was reduced. Expression of the cyclin-dependent kinase (CDK) inhibitor proteins p21 and p27 was enhanced. Consistent with the decreased cyclin D and increased p21/p27 expression, we found that phosphorylation of Rb was decreased at 39.5 degrees C. Cyclin A-, E- and Cdk2-associated histone H1 kinase activity was reduced concomitantly with the increase in p21 protein.
  
  
  CONCLUSIONS
  Decreased cyclin/Cdk kinase activity and decreased Rb phosphorylation are possible causes of G1 cell cycle arrest in tsBN462 cells at the restrictive temperature.
authors.affiliation: Molecular Biology and Virology Laboratory, Salk Institute, La Jolla, CA 92037, USA.
authors.forename: T
authors.initials: T
authors.lastname: Sekiguchi
authors.forename: E
authors.initials: E
authors.lastname: Noguchi
authors.forename: T
authors.initials: T
authors.lastname: Hayashida
authors.forename: T
authors.initials: T
authors.lastname: Nakashima
authors.forename: H
authors.initials: H
authors.lastname: Toyoshima
authors.forename: T
authors.initials: T
authors.lastname: Nishimoto
authors.forename: T
authors.initials: T
authors.lastname: Hunter
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D056741:Cyclin D; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D016213:Cyclins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D016193:G1 Phase / Q000235:genetics; D015870:Gene Expression; D017781:Genes, Immediate-Early; D051548:Histone Acetyltransferases; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics*; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D035381:TATA-Binding Protein Associated Factors; D013696:Temperature; D035362:Transcription Factor TFIID
chemical_list: D056741:Cyclin D; D016213:Cyclins; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D016160:Retinoblastoma Protein; D035381:TATA-Binding Protein Associated Factors; D035362:Transcription Factor TFIID; D051548:Histone Acetyltransferases; C069001:TATA-binding protein associated factor 250 kDa; D018844:Cyclin-Dependent Kinases