+-----------SUBJ:V-N----------+    
      +-----COMP:N-N(of)----+       |    
      |            +MOD_ATT:+       |    
      |            |        |       |    
 Requirement of nuclear proteins occurs .
COMP:N-N(of) (requirement,protein)
MOD_ATT:N-ADJ (protein,nuclear)
SUBJ:V-N (occur,requirement)