Grb2 and its apoptotic isoform Grb3-3 associate with heterogeneous nuclear ribonucleoprotein C, and these interactions are modulated by poly(U) RNA.
Grb2 is an adaptor molecule comprising one Src homology (SH) 2 and two SH3 domains. This protein has a natural isoform named Grb3-3 with a deletion within the SH2 domain. Numerous evidence points to a functional connection between SH2- and SH3-containing proteins and molecules implicated in RNA biogenesis. In this context, we have examined the binding of Grb2 and Grb3-3 to heterogeneous nuclear ribonucleoprotein (hnRNP) C. By the use of an in vivo genetic approach and through in vitro experiments, we furnish evidence that both Grb2 and Grb3-3 interact with hnRNP C proteins. Subcellular fractionation studies clearly show that Grb2 is partially localized in the nucleus. In addition, coimmunoprecipitation experiments demonstrate that Grb2.hnRNP C complexes exist in intact hematopoietic cells. The carboxyl-terminal SH3 domains of Grb2 and Grb3-3 are primarily responsible for the association with hnRNP C. However, although the proline-rich motif of hnRNP C is involved in the interaction with Grb2, it is not in the binding to Grb3-3. Furthermore, poly(U) RNA inhibits the association of Grb2 with hnRNP C, whereas it enhances the interaction between Grb3-3 and hnRNP C. These findings suggest that the Grb2/Grb3-3-hnRNP C interactions might fulfill different biological functions.
Romero
F
F
Institut Cochin de Génétique Moléculaire, U363 INSERM, Hôpital Cochin, 27 rue du faubourg Saint Jacques, 75014 Paris, France. romero@icgm.cochin.inserm.fr
Ramos-Morales
F
F
Domínguez
A
A
Rios
R M
RM
Schweighoffer
F
F
Tocqué
B
B
Pintor-Toro
J A
JA
Fischer
S
S
Tortolero
M
M
D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D017209:Apoptosis; D003001:Cloning, Molecular; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D016297:Mutagenesis, Site-Directed; D011072:Poly U / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D012332:RNA, Heterogeneous Nuclear / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D011506:Proteins; D012332:RNA, Heterogeneous Nuclear; D012261:Ribonucleoproteins; D011072:Poly U; D066246:ErbB Receptors