+MOD_ATT+SUBJ:V_PASS+COMP:V_PASS-N(+-COMP:N-N(of)+   
     |       |           |              |             |   
 __NODE__ protein is involved in differentiation of skin .
MOD_ATT:N-ADJ (protein,__NODE__)
SUBJ:V_PASS-N (involve,protein)
COMP:V_PASS-N(in) (involve,differentiation)
COMP:N-N(of) (differentiation,skin)