Exposure of goat uterine nuclei to estradiol in vitro results in an immediate exit of
ribonucleoproteins (RNP) from the nuclei to the medium. This RNP exit appears to be
mediated by an estrogen receptor localized in small nuclear ribonucleoproteins containing
U1 and U2 snRNA. Available evidence indicates that the estrogen receptor involved is not
the ERα, but an alternative form, which is also a 66 kDa protein. This is the nuclear estrogen
receptor II (nER‐II) that has no DNA‐binding capacity. The transport is estrogen‐specific …

Three proteins of a goat uterine small nuclear ribonucleoprotein (snRNP) fraction, which
bind to nuclear estrogen receptor‐II (nER‐II) have been isolated and purified. These are the
p32, p55, and p60 of which p32 is the major nER‐II binding protein. Indirect evidence
reveals that p32 binds to the nuclear export signal (NES) on the nER‐II. nER‐II is a snRNA
binding protein while p32 does not bind to the RNA. nER‐II along with p32 and p55 form an
effective Mg++ ATPase complex, the activation of which appears to be the immediate reason …