RAS, GTPase, and RAS-GAP

[stronghold]

I tried to search web, but did not find a simple explanation. I wanna understand how RAS is considered a proto-oncogene by producing GTPase? I know that GTPase hydrolyses GTP to GDP so decreases signal transduction.

Another point, NF1, tumor suppressor gene, works by producing RAS GTPase activating protein (RAS-GAP). I can understand that point as activation of GTPase would decrease GTP so no signal transduction.

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[Rac65]

To keep things simple - Ras activates downstream proteins responsible for regulation of transcription.
Ras itself has internal GTPase activity; when Ras binds GTP (instead of GDP) it becomes active and executes its purpose-in-life.
The activity of the Ras-GTP is autoregulated (as far as we're concerned, that's the main mechanism of downregulation) by hydrolysis of GTP to GDP (due to its GTPase subunit) thereby decreasing the activity of Ras.
Failure to hydrolize the GTP in GTP-Ras (mutation in the GTPase domain) creates an "always on" GTP-Ras, thereby promoting oncogenesis.

It's basically suppressing (mutation) an inhibitor (GTPase) which produces overactivation.

P.S - this is just one of the possible mutations in Ras.