C. Isaac et al., NOPP140 FUNCTIONS AS A MOLECULAR LINK BETWEEN THE NUCLEOLUS AND THE COILED BODIES, The Journal of cell biology, 142(2), 1998, pp. 319-329
Coiled bodies are small nuclear organelles that are highly enriched in
small nuclear RNAs, and that have long been thought to be associated
with the nucleolus. Here we use mutational analysis, transient transfe
ctions, and the yeast two-hybrid system to show that the nucleolar pho
sphoprotein Nopp140 functions as a molecular Ink between the two promi
nent nuclear organelles. Exogenous Nopp140 accumulated in the nucleolu
s rapidly, but only after a lag phase in coiled bodies, suggesting a p
athway between the two organelles. The expression of partial Nopp140 c
onstructs exerted dominant negative effects on the endogenous Nopp140
by chasing it and other antigens that were common to both organelles o
ut of the nucleolus. The alternating positively and negatively charged
repeat domain of Nopp140 was required for targeting to both organelle
s. In addition, partial Nopp140 constructs caused formation of novel s
tructures in the nucleoplasm and, in the case of the conserved carboxy
terminus, led to the dispersal of coiled bodies. As a final link, we
identified the coiled body-specific protein p80 coilin in a yeast two-
hybrid screen with Nopp140. The interaction of the two proteins was co
nfirmed by coimmunoprecipitation. Taken together, Nopp140 appeared to
shuttle between the nucleolus and the coiled bodies, and to chaperone
the transport of other molecules.