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Ostip2, a novel oncoprotein that associates with the Rho exchange factor Ost
R Yamanaka1, R Blumenthal, M V Lorenzi
1Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
The ost protooncogene encodes a guanine nucleotide exchange factor for the Rho family of small GTPases, RhoA and Cdc42. The N-terminal domain of Ost (Ost-N) appears to negatively regulate the oncogenic activity of the protein, as deletion of this domain drastically increases its transforming activity in NIH 3T3 cells. Using a yeast two-hybrid system, we identified five genes encoding proteins that can interact with Ost-N. One of them, designated OSTIP2 (Ost interacting protein 2), encoded a previously uncharacterized protein. The OSTIP2 product is highly expressed in skeletal muscle as a 1.2-kb transcript. Full-length OSTIP2 cDNA contained an ORF of 193 amino acids. Transcription-coupled translation of OSTIP2 cDNA in reticulocyte lysates revealed a protein product of 20 kDa, which corresponded to the predicted size of the protein. Bacterially expressed glutathione S-transferase (GST)-Ostip2 fusion protein efficiently associated in vitro with baculovirus-expressed Ost. Interestingly, expression of Ostip2 in NIH 3T3 cells efficiently induced foci of morphologically transformed cells. Moreover, inoculation of athymic (nude) mice with OSTIP2 transfectants strongly induced tumor formation. These results suggest that Ostip2 is a novel oncoprotein that can interact with the Rho exchange factor Ost.
Insights
Researchers discovered OSTIP2, a novel oncoprotein interacting with the Ost protooncogene. OSTIP2 promotes cell transformation and tumor formation, highlighting its oncogenic potential in cancer research.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- The ost protooncogene encodes a guanine nucleotide exchange factor for Rho GTPases.
- The N-terminal domain of Ost negatively regulates its oncogenic activity.
Purpose of the Study:
- To identify proteins interacting with the N-terminal domain of Ost.
- To characterize the function and oncogenic potential of a novel interacting protein, OSTIP2.
Main Methods:
- Yeast two-hybrid system to identify interacting proteins.
- In vitro binding assays (GST pull-down).
- Cell transformation assays in NIH 3T3 cells and tumor induction in nude mice.
Main Results:
- Identified OSTIP2 as an Ost-interacting protein highly expressed in skeletal muscle.
- OSTIP2 induced morphological transformation of NIH 3T3 cells.
- OSTIP2 transfection led to significant tumor formation in athymic mice.
Conclusions:
- OSTIP2 is a novel oncoprotein that interacts with the Rho exchange factor Ost.
- OSTIP2 possesses oncogenic activity, promoting cell transformation and tumorigenesis.