There are many MMA fighters that can box.
Vitali Klitschko,"JDS is a very strong fighter, deserves to be champ, he jabs like my brother Wladimir, so he is learning from the best."

Junior Dos Santos is a great boxer and his boxing has helped him become the HW champ, absolutely outclassing anyone who has stood with him.
He is a really good example of how to use boxing in MMA.