Ask Mr. Smarty Plants

American beautyberry (Callicarpa americana) is a wonderful shrub for a partly shaded site and has such beautiful iridescent purple berries in the fall. Here's some information from the wildflower.org website:

American beautyberry is a wonderful, large understory shrub with a naturally loose and graceful arching form. In the fall and early winter, the branches are laden with magenta purple (sometimes white) berry clusters that look spectacular as the leaves drop in autumn. It is useful as a screen in swampy or wooded locations or under shade trees in a garden setting. It can be cut to 12 above the base each winter to encourage more compact growth, flowers and fruit. It can also be left to mature naturally into a tall woody shrub. The shrub may temporarily defoliate and lose developing fruit during periods of prolonged summer drought.

Notice that the shrub may drop leaves if it gets too dry during the summer.  It does prefer to grow in moist, rich wooded bottomlands or along swamp edges. Perhaps a little more water will help the shrub since it is in a fairly sunny site (with 5 hours of sun). In any case, have patience to see if the leaves regrow on the affected branch next spring. If they don't then prune out that section and observe the rest of the plant for any further signs. If there is more dieback then perhaps moving the shrub to a shadier site is needed.