+------------SUBJ:V-N------------+                   
      +----COMP:N-N(of)---+            +-COMP:V-N(in)-+    
      |           +MOD_ATT+            |        +MOD_A+    
      |           |       |            |        |     |    
 Expression of __SP__ __NODE__ gene occurs in HepG2 cells .
COMP:N-N(of) (expression,__NODE__)
MOD_ATT:N-ADJ (__NODE__,__SP__)
SUBJ:V-N (occur,expression)
COMP:V-N(in) (occur,cell)
MOD_ATT:N-N (cell,HepG2)