SQL & PL/SQL :: Cursor Select For Update / Multiple Columns Of Different Tables

i have two tables test1 and test2. i want to update the column(DEPT_DSCR) of both the tables TEST1 and TEST2 using select for update and current of...using cursor.

I have a code written as follows :

DECLARE
v_mydept1 TEST1.DEPT_CD%TYPE;
v_mydept2 TEST2.DEPT_CD%TYPE;
CURSOR C1 IS SELECT TEST1.DEPT_CD,TEST2.DEPT_CD FROM TEST1,TEST2 WHERE TEST1.DEPT_CD = TEST2.DEPT_CD AND TEST1.DEPT_CD = 'AA' FOR UPDATE OF TEST1.DEPT_DSCR,TEST2.DEPT_DSCR;
[code].......

The above code when run says that it runs successfully. But it does not updates the desired columns[DEPT_DSCR].

It only works when we want to update single or multiple columns of same table...i.e. by providing these columns after "FOR UPDATE OF"
I am not sure what is the exact problem when we want to update multiple columns of different tables.