+------------SUBJ:V-N------------+              
      +-------COMP:N-N(of)-------+     |              
      |           +-MOD_ATT:N-ADJ+     |              
      |           |       +MOD_AT+     |              
      |           |       |      |     |              
 Expression of __SP__ __NODE__ mRNA occurs in kidney .
COMP:N-N(of) (expression,mRNA)
MOD_ATT:N-ADJ (mRNA,__SP__)
MOD_ATT:N-ADJ (mRNA,__NODE__)
SUBJ:V-N (occur,expression)