
The work described
below is carried out in close collaboration with the laboratory of Dr. Ron
Patterson (Department of Microbiology and Molecular Genetics).
The research
interests of our laboratories are focused on two carbohydrate-binding proteins,
galectin-1 and galectin-3. The galectins comprise a family of galactose-binding
proteins that share characteristic amino acid sequences in the carbohydrate
recognition domain of the polypeptides. Our interest in this system stemmed
from the observation that galectin-3 was found as a ribonucleoprotein complex
in the nucleus. Using nuclear extracts derived from HeLa cells, capable
of carrying out splicing of pre-mRNA in a cell-free assay, depletion and
reconstitution experiments demonstrated that galectins-1 and -3 are splicing
factors. More recently, we have documented that galectins-1 and -3 both
independently bind to a protein designated Gemin4. The significance of this
finding lies in the fact that other investigators had shown that Gemin4
is one component of a macromolecular complex, the SMN complex, that plays
important roles in the biogenesis, delivery, and regeneration of small nuclear
ribonucleoprotein particles (snRNPs) for spliceosome assembly. On the basis
of these and other observations, the immediate objectives of our research
include:
(a) to delineate and characterize the components and interactions
of the ribonucleoprotein complex on which galectins-1 and -3 have been found;
(b) to define the step(s) during which galectins-1 and -3 participate in
splicing;
(c) to test, by site-directed mutagenesis, whether carbohydrate-binding
is required for the role of; galectins in the splicing reaction;and
(d)
to study the nucleo-cytoplasmic shuttling properties of galectin-3, in terms
of import and export signals and in terms of a possible role in mRNA transport.
Arnoys, E.A. and Wang, J.L. (2007) Dual localization: proteins in extracellular and intracellular compartments. Acta Histochemica 109: 89-110.
Wang, W.Z., Park, J.W., Wang, J.L., and Patterson, R.J. (2006) Immunoprecipitation of spliceosomal RNAs by antisera to galectin-1 and galectin-3. Nucleic Acids Res. 34: 5166-5174.
Li, S.-Y., Davidson, P.J., Patterson, R.J., Wang, J.L., and Arnoys, E.J. (2006) Transport of Galectin-3 between the Nucleus and Cytoplasm. II. Identification of the Signal for Nuclear Export. Glycobiology 16: 612-622 .
Davidson, P.J., Li, S.-Y., Pearson, A., Vandergaast, R., Verde, E., Patterson, R.J., Wang, J.L., and Arnoys, E.J. (2006) Transport of Galectin-3 between the Nucleus and Cytoplasm. I. Conditions and Signals for Nuclear Import, Glycobiology 16: 602-611.