This month's issue of MSDN magazine has a good article: http://msdn.microsoft.com/en-us/magazine/hh852595.aspx.
However, when you used the phrase "tying the UI to the game's backend" and the word "architecture", I'm thinking that you need more information beyond simply binding from a XAML view to an object behind it. I'm thinking you should start reading about MVVM, as well as general WP7 architecture guidance.
There's stuff all over the web but the problem is that the overall guidance is not fully prescriptive in all cases - MS has advice for you, but no silver bullet. This makes it hard to pull any useful information out of all the noise on message boards and places like StackOverflow (not implying that there aren't good answers out there, but you will find many that are conflicting, overly confusing or tailored to specific scenarios.)
In my opinion, the best way to get started is with the publications from MS Patterns and Practices. Hit that link and Ctrl-F for "phone" and get to reading. Even the "retired" Windows Phone 7 Developer Guide there is great, but I'd start at the top with the Phone/MVVM one. Check out the Resources in that one, including Karl's "MVVM In the Box". And make sure you actually download and study the code as well as reading the article.