Ive never hunted Alaska, but on my Caribou trip to Canada I wore Duofold (sp?) long underwear, a pair of lightweight wool hunting pants from Cabelas, and a pair of Gore-Tex rain pants from L.L. Beans. I was very comfortable on the entire trip with this set-up. For colder weather, Id simply switch to a heavier weight wool pant for that particular layer. Im sure some of the regular Alaskan hunters will have better suggestions, but this is a start at least.
Good luck!