Suppression of tumorigenicity in human colon carcinoma cells by introduction of normal chromosome 5 or 18
Article Abstract:
Deletions of areas on several chromosomes (structures that contain the genetic information of the cell), including the area on chromosome 5 known as 5q, and the area on chromosome 18 known as 18q, have been associated with the development of colon cancer. Two genes that are thought to be tumor suppressors, genes that inhibit the development of tumors, have been identified on both these chromosomes: the APC gene on 5q, and the DCC gene on 18q. To study the role of these genes in the deleted regions, normal human chromosomes were introduced into cancerous human colon cells. This was accomplished by binding normal chromosomes 5, 18, and 11 (as a control) to the cancer cells. With the introduction of the normal chromosomes 5 and 18, the physical shape and size of the cancerous cells changed. The cancerous cells were spindle-shaped. With the introduction of chromosome 5, the cells became polygonal in shape and closely packed, similar to normal cells. Cells that received chromosome 18 became flattened. The addition of chromosome 11 did not change the morphology of the cells from the cancerous cells. The cells containing chromosome 5 and 18 did not grow as well as the cancerous cells in tissue culture and did not cause tumors when injected into mice, while the cancerous cells without the additional chromosomes or with chromosome 11 caused tumors. This study strongly suggests that chromosome 5 and 18 contain tumor suppressor genes that inhibit the development of colon cancer. Introducing normal genes by inserting normal chromosomes caused the suppression of the characteristics of cancerous cells. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1991
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Rhodopsin activation blocked by metal-ion-binding sites linking transmembrane helices C and F
Article Abstract:
An experiment was conducted to determine the transmission mechanics of sensory signals across the plasma membrane to the heterotrimeric G proteins. Several metal-ion-binding sites were engineered between transmembrane helices (TM) to prevent activation-induced conformation change in specific locations. Histidine residues were substituted for natural amino acids at the cytoplasmic ends of the TM helices C and F. Despite the absence of the natural amino acids, visual G protein activation occurred. The results suggest that the TM helices C and F are in close proximity and indicate that the movements of these helices are important for transducin activation.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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