+----------COMP:V-N(in)----------+    
      +--------------SUBJ:V-N-------------+              +--MOD_ATT:N-ADJ--+    
      +----COMP:N-N(of)---+               |              |         +MOD_ATT+    
      |           +MOD_ATT+          +-NEG+              |         |   +MOD+    
      |           |       |          |    |              |         |   |   |    
 Expression of __SP__ __NODE__ does not occur in undifferentiated 3T3 L1 cells .
COMP:N-N(of) (expression,__NODE__)
MOD_ATT:N-ADJ (__NODE__,__SP__)
SUBJ:V-N (occur,expression)
NEG (occur,not)
COMP:V-N(in) (occur,cell)
MOD_ATT:N-ADJ (cell,undifferentiated)
MOD_ATT:N-ADJ (cell,3T3)
MOD_ATT:N-N (cell,L1)