Read the sentence.

My brother who is a superb actor will audition tomorrow for a film role.

How should the writer punctuate the underlined nonrestrictive clause in order to emphasize it?

My brother: who is a superb actor will audition tomorrow for a film role.
My brother; who is a superb actor; will audition tomorrow for a film role.
My brother who is a superb actor, will audition tomorrow for a film role.
My brother—who is a superb actor—will audition tomorrow for a film role.