+------SUBJ:V-N------+              
      +COMP:N-N(of)+       +COMP:V-N(+    
      |            |       |         |    
 Expression of __NODE__ occurs in spleen .
COMP:N-N(of) (expression,__NODE__)
SUBJ:V-N (occur,expression)
COMP:V-N(in) (occur,spleen)