Region-encoding on xbox360 version?

Questions:

1. Is the Xbox360 version region locked?
2. Is DLC region locked?

I
live in the US, moved here few months ago and brought my UK Xbox and
TV with me. I pre-ordered the UK Xbox CE (just in case it was
region-locked) and cant wait for it to arrive...but it just occured to
me that the DLC may be region encoded as well, which would be rather
annoying.

Does anyone know?
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