+----------SUBJ:V-N----------+                 
                   +----COMP:N-N(of)----+       +COMP:V-N(in)+    
       +MOD_ATT:N-A+            +MOD_ATT+       |       +MOD_+    
       |           |            |       |       |       |    |    
 Constitutive expression of __NODE__ protein occurs in NB4 cells .
MOD_ATT:N-ADJ (expression,constitutive)
COMP:N-N(of) (expression,protein)
MOD_ATT:N-ADJ (protein,__NODE__)
SUBJ:V-N (occur,expression)
COMP:V-N(in) (occur,cell)
MOD_ATT:N-N (cell,NB4)