Google created the V8 JavaScript engine: V8 compiles JavaScript source code directly into machine code when it is first executed.
Node.js is built on V8 - why is Google not offering any Node.js servers like Microsoft Azure?
Google App Engine would be a natural place to put Node.js.
Do you know why Google is not doing just that?
Node.js is maintained by Joyent, who is in a way a competitor of Google.
Node.js has no link what so ever with Google but is in fact built on top of an open source project started by Google.
Google might jumped into this business just like Azure did, but there are already so many PaaS doing it, it might not be worth it. I have never used GAE, but my understanding is that it is quite different that other PaaS and you have to use GAE libraries to make your code run.
Which, this is my personal feeling, is not really what the Node.js community is looking for. Node.js is used to quickly make a fast lightweight app, a big share for APIs for Phone apps for example.
Nevertheless if you are looking for a PaaS for Node.js, the are quite a few out there:
Those are just some names off the top of my head. There quite a few but those are the major ones. Oh there is Heroku too, but they don't have support for WebSocket which is a bummer for any Socket.IO based app.