+----------------SUBJ:V-N----------------+                             
      +-------COMP:N-N(of)-------+             +------COMP:V-N(in)------+    
      |           +-MOD_ATT:N-ADJ+             |          +MOD_ATT:N-ADJ+    
      |           |       +MOD_AT+        +-NEG+          |      +MOD_AT+    
      |           |       |      |        |    |          |      |      |    
 Expression of __SP__ __NODE__ mRNA does not occur in salivary gland tissue .
COMP:N-N(of) (expression,mRNA)
MOD_ATT:N-ADJ (mRNA,__SP__)
MOD_ATT:N-ADJ (mRNA,__NODE__)
SUBJ:V-N (occur,expression)
NEG (occur,not)
COMP:V-N(in) (occur,toilet)
MOD_ATT:N-ADJ (toilet,salivary)
MOD_ATT:N-N (toilet,gland)