  We present updates to a recent CTEQ-Jefferson Lab (CJ) global analysis of
parton distribution functions with a new set of electroweak data that provide
unique access to quark flavor separation in the proton. In particular, recent
$W$ and $Z$ boson measurements from the STAR experiment at RHIC put additional
constraints on light quarks and antiquarks near the valence regime. The new
measurement of the Drell-Yan lepton pair production ratio in $p+p$ and $p+d$
collisions by the SeaQuest experiment at Fermilab extends the large-$x$
coverage of the previous E866 experiment and sheds new light on the light
antiquarks distribution. In this report, the impact of these new data sets on
parton distribution functions will be presented with emphasis given to the
flavor asymmetry of the light antiquark sea at large values of the parton
momentum $x$.
