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Binding of NCK to SOS and activation of ras-dependent gene expression
1Daiichi Research Center, Cardiovascular Research Institute, University of California at San Francisco 94143.
Abstract:
NCK, an SH2- and SH3 domain-containing protein, becomes phosphorylated and associated with tyrosine kinase receptors upon growth factor stimulation. The sequence of NCK suggests that NCK functions as a linker between receptors and a downstream signaling molecule. To determine if NCK can mediate growth factor-stimulated responses, we measured the ability of NCK to activate the fos promoter. We found that in NIH 3T3 cells, NCK strongly activates this promoter. The effect of NCK on the fos promoter is enhanced by c-ras and blocked by dominant negative ras. We also found that NCK binds directly to the guanine nucleotide exchange factor SOS. This interaction is mediated by the SH3 domains of NCK. These findings suggest that NCK can regulate p21ras-dependent gene transcription through interaction with SOS protein.
Insights
NCK protein links growth factor receptors to downstream signaling. It activates the fos promoter and interacts with SOS, suggesting a role in ras-dependent gene transcription.
Area of Science:
- Molecular Biology
- Cell Signaling
- Biochemistry
Background:
- NCK is an SH2- and SH3 domain-containing protein.
- NCK associates with tyrosine kinase receptors after growth factor stimulation.
- NCK's structure suggests a role as a linker in cellular signaling pathways.
Purpose of the Study:
- To investigate the role of NCK in mediating growth factor-stimulated responses.
- To determine if NCK can activate the fos promoter.
- To explore NCK's interaction with downstream signaling molecules like ras and SOS.
Main Methods:
- Activation of the fos promoter by NCK in NIH 3T3 cells was measured.
- The effect of NCK on the fos promoter in the presence of c-ras and dominant-negative ras was assessed.
- Direct binding between NCK and the guanine nucleotide exchange factor SOS was examined, focusing on the role of NCK's SH3 domains.
Main Results:
- NCK strongly activates the fos promoter in NIH 3T3 cells.
- NCK-mediated fos promoter activation is enhanced by c-ras and inhibited by dominant-negative ras.
- NCK directly binds to SOS, with the SH3 domains of NCK mediating this interaction.
Conclusions:
- NCK functions as a critical mediator in growth factor signaling pathways.
- NCK plays a role in regulating p21ras-dependent gene transcription.
- NCK's interaction with SOS is a key mechanism for its signaling function.