The TSC1 gene product, hamartin, negatively regulates cell proliferation.
Tuberous sclerosis is an autosomal dominant hereditary disease caused by mutations in either the TSC1 or the TSC2 tumor suppressor gene. The TSC1 gene on chromosome 9q34 encodes a 130 kDa protein named hamartin, and the TSC2 gene on chromosome 16p13.3 codes for tuberin, a 200 kDa protein. Here we show that expression of hamartin, assayed by immunoblot analyses, is high in G(0)-arrested cells and hamartin is expressed throughout the entire ongoing cell cycle. An interaction of hamartin and tuberin can be detected in every phase of the cell cycle. Ectopic expression of high levels of hamartin attenuates cellular proliferation. We provide evidence that this effect could depend on a coiled-coil region earlier proposed to be involved in binding of hamartin to tuberin. Further investigations revealed that hamartin affects cell proliferation via deregulation of G(1) phase. Our data have a clear impact on understanding the role of hamartin during development of this disease.
Obstetrics and Gynecology, University of Vienna, Prenatal Diagnosis and Therapy, Währinger Gürtel 18-20, A-1090 Vienna, Austria.
A
A
Miloloza
M
M
Rosner
M
M
Nellist
D
D
Halley
G
G
Bernaschek
M
M
Hengstschläger
D000818:Animals; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002455:Cell Division; D002460:Cell Line; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016147:Genes, Tumor Suppressor; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D012097:Repressor Proteins / Q000378:metabolism; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins
C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D011506:Proteins; D012097:Repressor Proteins; C000624650:TSC1 protein, human; C000624653:TSC2 protein, human; C000624652:Tsc1 protein, rat; C000624655:Tsc2 protein, rat; D000077004:Tuberous Sclerosis Complex 1 Protein; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27