Alpha B-crystallin is a small heat shock protein.
Sequence similarity between alpha B-crystallin and small heat shock proteins (HSPs) has prompted us to investigate whether alpha B-crystallin expression is induced by heat shock. Indeed, accumulation of alpha B-crystallin was detected immunologically in NIH 3T3 cells after incubation at elevated temperatures and after addition of Cd2+ or sodium arsenite to these cells. Two-dimensional gel electrophoresis revealed identity between alpha B-crystallin from eye lenses and from heat-treated fibroblasts. The promoter of the alpha B-crystallin gene was fused to the bacterial chloramphenicol acetyltransferase gene and was shown to confer heat inducibility on this reporter gene in transient transfection assays. A perfect heat shock element within the promoter region is likely to mediate this response. Small HSPs and alpha B-crystallin were shown to share the following two physical properties: (i) they form supramolecular structures with sedimentation values around 17 S and (ii) they are associated with the nucleus at high temperatures and are localized in the cytoplasm under normal conditions. We conclude that alpha B-crystallin has to be considered a member of the class of small HSPs.
Klemenz
R
R
Division of Cancer Research, University of Zurich, Switzerland.
Fröhli
E
E
Steiger
R H
RH
Schäfer
R
R
Aoyama
A
A
D000818:Animals; D001483:Base Sequence; D002451:Cell Compartmentation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003459:Crystallins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics*; D046911:Macromolecular Substances; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D014158:Transcription, Genetic
D003459:Crystallins; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances