How to make F1/F2/F3/F4 usable in screen emacs?

[pei . linux]

Hi Dear friends,
I try to use emacs under screen environment, I bind some oftenly used function 
to F1/F2/F3/F4 under
emacs, when I try to
use these, it seems not work. Can anyone help me on this? Thanks a lot. :)

Here is my .screenrc file:
------------------BEGIN----------------------
#kill startup message
startup_message off

defflow off

# define a bigger scrollback, default is 100 lines, I like large scrollback
defscrollback 1024

# An alternative hardstatus to display a bar at the bottom listing the
# windownames and highlighting the current windowname in blue. (This is only
# enabled if there is no hardstatus setting for your terminal)
hardstatus on
hardstatus alwayslastline
hardstatus string "%{.bW}%-w%{.rW}%n %t%{-}%+w %=%{..G} %H %{..Y} %m/%d %C%a "
# caption always "%?%F%{-b 4w}%:%{-b bb}%? %H | %l | %m-%d %c |%?%F%{-b 
4w}%?%L=%-Lw%45>%{-b
w4}%n%f* %t%{-}%+Lw%-0<"

# key bingdings
# remove some stupid/dangerous key bindings
bind k
bind ^k
bind .
bind ^\
bind \\
bind ^h
bind h
bind l windowlist
bindkey ^[, prev      # use Alt+, to show preview screen window
bindkey ^[. next      # use Alt+. to show next screen window

# Our warning of activity
activity "Activity in %t(%n)"

# Escape key is C-z.  (I use C-a too much in Emacs.)
#escape ^zz
# Escape key is `  (I use C-a too much in Emacs)
escape ``
--------------------------END----------------------------