A4s

[Mister Z]

I'm not sure if I like A4s as an isolating hand with a LAP and an unknown still to act. I like the flop because I think the 3-bet will persuade Button to fold his 4-6 outer on the turn. The river is really weird... I don't know if raising wins you a pot you might have lost 1 in 7-or-so times, but I would think raising folds Button out at least 60-70% of the time. Two other considerations -

1) Your kicker situation might have just been solved by the board pairing. This increases the chance that at least you're getting a chop with Button.
2) A lot of bad players see the board pair and think "hey I've got 2-pair, that's a great hand." If we think this is slightly significant, the chance YHIG against MP1 goes up.

Taken the size of the pot I'll vote for a raise on the river.