Study on roles of RCC1 and nuclear small G proteins (Ran and RagA) in cell growth.

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In this study, following results were obtained during the term, Rag A interacting proteins were obtained with the yeast two hybrid method. Rag C and Rag D were bound to Rag A in the cell lysate and were shown to form heterodimer with Rag A in cells. The C-terminal regions of Rag C and Rag D were found to be bound to the C-terminal region of Rag A.Rag C and Rag D proteins had 6 percent similarity with Rag A protein. Rag C protein had 72 percent similarity with Rag D protein. Rag C and Rag D were shown to be localized in both in the cytoplasm and the nucleus in cells by the indirect immunofluorescence and were colocalized with Rag A.Rag C were shown to be a GTP-binding protein. A novel 227 and 158 proteins were identified to interact with Rag A.The C-terminal region of the 221 protein interacted with leucine zipper region of the Rag A protein. The 227 protein interacted with GTP form of Rag A, but not with GDP form of Rag A.Thus, the 227 protein is a candidate of a effector protein of Rag A.the 227 protein was colocalized with RNPS 1 and CLK1 in the nucleus.Study of RCC1 phosphorylation were performed. RCC1 was found to be labeled with radiolabeled P-32 in human cells.Amino terminal region of RCC1 was found to be the region of phosphorylation. Introduction of mutation in this region inhibited entry of RCC1 into nucleus.