The second word in each of the following pairs is derived from the first word according to a certain pattern. That pattern can be explained by a classic five-word phrase. What's the phrase?

MOUNT - MOMENT
HOUR - HOMER
SUE - SMEE
FRAUD - FRAMED

HINTS:
1. Notice that there is a U in each first word.
2. Notice that there is an ME in each second word. 
3. The phrase is a classic breakup line.

Answer:

The letter U in the first word is replaced by ME in the second word:
IT'S NOT YOU, IT'S ME.

Credit: Daniel A. Finan