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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Galectin-3 (M(r) approximately 35,000) is a galactose/lactose-specific lectin found in association with ribonucleoprotein complexes in many animal cells. Cell-free-splicing assays have been carried out to study the requirement for galectin-3 in RNA processing by HeLa cell nuclear extracts by using 32P-labeled MINX as the pre-mRNA substrate. Addition of saccharides that bind galectin-3 with high affinity inhibited product formation in the splicing assay, while addition of carbohydrates that do not bind to the lectin did not inhibit product formation. Nuclear extracts depleted of galectin-3 by affinity adsorption on a lactose-agarose column were deficient in splicing activity. Extracts subjected to parallel adsorption on control cellobiose-agarose retained splicing activity. The activity of the galectin-3-depleted extract could be reconstituted by the addition of purified recombinant galectin-3, whereas the addition of other lectins, either with a similar saccharide binding specificity (soybean agglutinin) or with a different specificity (wheat germ agglutinin), did not restore splicing activity. The formation of splicing complexes was also sensitive to galectin-3 depletion and reconstitution. Together, these results define a requirement for galectin-3 in pre-mRNA splicing and identify it as a splicing factor.
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PMID:Identification of galectin-3 as a factor in pre-mRNA splicing. 786 63

Galectins are a family of beta-galactoside-binding proteins that contain characteristic amino acid sequences in the carbohydrate recognition domain (CRD) of the polypeptide. The polypeptide of galectin-1 contains a single domain, the CRD. The polypeptide of galectin-3 has two domains, a carboxyl-terminal CRD fused onto a proline- and glycine-rich amino-terminal domain. In previous studies, we showed that galectin-3 is a required factor in the splicing of nuclear pre-mRNA, assayed in a cell-free system. We now document that (i) nuclear extracts derived from HeLa cells contain both galectins-1 and -3; (ii) depletion of both galectins from the nuclear extract either by lactose affinity adsorption or by double-antibody adsorption results in a concomitant loss of splicing activity; (iii) depletion of either galectin-1 or galectin-3 by specific antibody adsorption fails to remove all of the splicing activity, and the residual splicing activity is still saccharide inhibitable; (iv) either galectin-1 or galectin-3 alone is sufficient to reconstitute, at least partially, the splicing activity of nuclear extracts depleted of both galectins; and (v) although the carbohydrate recognition domain of galectin-3 (or galectin-1) is sufficient to restore splicing activity to a galectin-depleted nuclear extract, the concentration required for reconstitution is greater than that of the full-length galectin-3 polypeptide. Consistent with these functional results, double-immunofluorescence analyses show that within the nucleus, galectin-3 colocalizes with the speckled structures observed with splicing factor SC35. Similar results are also obtained with galectin-1, although in this case, there are areas of galectin-1 devoid of SC35 and vice versa. Thus, nuclear galectins exhibit functional redundancy in their splicing activity and partition, at least partially, in the nucleoplasm with another known splicing factor.
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PMID:Evidence for a role for galectin-1 in pre-mRNA splicing. 923 29

Using both conventional and laser confocal fluorescence microscopy, the intracellular distribution of galectin-1 in HeLa cells was analyzed and compared with the localization of previously documented markers of the nucleus and cytoplasm. The Sm epitopes of the small nuclear ribonucleoprotein complexes (snRNPs) and the non-snRNP splicing factor SC35 yielded only nuclear staining. On the other hand, the enzyme lactate dehydrogenase was cytoplasmic. In contrast to these patterns in which nuclear versus cytoplasmic localizations appeared to be mutually exclusive, galectin-1, as well as galectin-3, yielded simultaneous nuclear and cytoplasmic staining. Confocal microscopy showed galectin-1 fluorescence throughout most of the sections from the top of the cell to the bottom. Through the middle sections, as the plane of focus cuts through the nucleus, there was definite fluorescence staining in the nuclear compartment. This nuclear localization was critically dependent on the type of detergent used to permeabilize the cell: cells treated with saponin or digitonin yielded exclusively cytoplasmic staining while Triton X-100-treated cells showed nuclear as well as cytoplasmic labeling. Finally, double-immunofluorescence analysis showed that, within the nucleoplasm, the following pairs of nuclear antigens could be colocalized in certain speckled structures: (a) SC35 versus Sm; (b) galectin-1 versus Sm; (c) galectin-3 versus Sm; and (d) galectin-1 versus galectin-3. These results establish the presence of galectin-1 in the nuclei of HeLa cells, a conclusion consistent with the identification of the protein in nuclear extracts of the same cells and with its documentation as a factor in pre-mRNA splicing.
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PMID:A comparative nuclear localization study of galectin-1 with other splicing components. 968 29

The hypoxia-inducible factor 1 (HIF-1) plays a critical role in cellular responses to hypoxia. The aim of the present study was to evaluate which genes are induced by hypoxia, and whether this induction is mediated by HIF-1, by expression microarray analysis of wt and HIF-1alpha null mouse fibroblasts. Forty-five genes were up-regulated by hypoxia and 40 (89%) of these were regulated by HIF-1. Of the 114 genes down-regulated by hypoxia, 19 (17%) were HIF-1-dependent. All glycolytic enzymes were strongly up-regulated by hypoxia in a HIF-1-dependent manner. Genes already known to be related to hypoxia, such as glucose transporter 1, BNIP3, and hypoxia-induced gene 1, were induced. In addition, multiple new HIF-1-regulated genes were identified, including genes involved in metabolism (adenylate kinase 4, galactokinase), apoptosis (galectin-3 and gelsolin), and invasion (RhoA). Genes down-regulated by hypoxia were involved in cytoskeleton maintenance (Rho kinase), mRNA processing (heterogeneous nuclear ribonucleoprotein H1 and splicing factor), and DNA repair (REV3). Furthermore, seven cDNAs from genes with unknown function or expressed sequence tags (ESTs) were up-regulated and 27 such cDNAs were down-regulated. In conclusion, hypoxia causes down- rather than up-regulation of gene expression and HIF-1 seems to play a major role in the regulation of hypoxia-induced genes.
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PMID:Up-regulation of gene expression by hypoxia is mediated predominantly by hypoxia-inducible factor 1 (HIF-1). 1590 72

Although members of the serine (S)- and arginine (R)-rich splicing factor family (SR proteins) were initially purified on the basis of their splicing activity in the nucleus, there is recent documentation that they exhibit carbohydrate-binding activity at the cell surface. In contrast, galectins were isolated on the basis of their saccharide-binding activity and cell surface localization. Surprisingly, however, two members (galectin-1 and galectin-3) can be found in association with nuclear ribonucleoprotein complexes including the spliceosome and, using a cell-free assay, have been shown to be required splicing factors. Thus, despite the difference in terms of their original points of interest, it now appears that members of the two protein families share four key properties: (a) nuclear and cytoplasmic distribution; (b) pre-mRNA splicing activity; (c) carbohydrate-binding activity; and (d) cell surface localization in specific cells. These findings provoke stimulating questions regarding the relationship between splicing factors in the nucleus and carbohydrate-binding proteins at the cell surface.
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PMID:SR proteins and galectins: what's in a name? 2057 10