Abstract
BackgroundThe human retinoblastoma susceptibility gene encodes a nuclear phosphoprotein RB, which is a negative regulator of cell proliferation. The growth suppression function of RB requires an evolutionarily conserved A/B domain that contains two distinct peptide-binding pockets. At the A/B interface is a binding site for the C-terminal trans-activation domain of E2F. Within the B-domain is a binding site for proteins containing the LxCxE peptide motif.Methodology/Principle FindingsBased on the crystal structure of the A/B domain, we have constructed an RB-K530A/N757F (KN) mutant to disrupt the E2F- and LxCxE-binding pockets. The RB-K530A (K) mutant is sufficient to inactivate the E2F-binding pocket, whereas the RB-N757F (N) mutant is sufficient to inactivate the LxCxE-binding pocket. Each single mutant inhibits cell proliferation, but the RB-KN double mutant is defective in growth suppression. Nevertheless, the RB-KN mutant is capable of reducing etoposide-induced apoptosis.Conclusion/SignificancePrevious studies have established that RB-dependent G1-arrest can confer resistance to DNA damage-induced apoptosis. Results from this study demonstrate that RB can also inhibit apoptosis independent of growth suppression.
Highlights
The retinoblastoma susceptibility gene (RB1) encodes a nuclear phosphoprotein RB with tumor suppression function [1]
The RB and mutant proteins were expressed in the RB-deficient breast cancer cell line MBA-MD468 through adenoviral-mediated gene transfer, and lysates from the adenovirus-infected cells were applied to glutathione-agarose beads loaded with GST-E2F1 or GST-E7 recombinant proteins purified from bacteria (Fig. 1B)
The RB-K mutant does not bind to the C-terminal trans-activation domain of E2F and it does not inhibit the transactivation function of E2F1
Summary
The retinoblastoma susceptibility gene (RB1) encodes a nuclear phosphoprotein RB with tumor suppression function [1]. The current knowledge suggests that RB suppresses tumor development by inhibiting cell proliferation and promoting terminal differentiation [1]. The E2F transcription factors regulate genes required for cell proliferation and apoptosis [5]. By inhibiting E2F-dependent transcription, RB negatively regulates cell proliferation and apoptosis. The human retinoblastoma susceptibility gene encodes a nuclear phosphoprotein RB, which is a negative regulator of cell proliferation. The growth suppression function of RB requires an evolutionarily conserved A/B domain that contains two distinct peptide-binding pockets. Within the B-domain is a binding site for proteins containing the LxCxE peptide motif. Each single mutant inhibits cell proliferation, but the RB-KN double mutant is defective in growth suppression. Results from this study demonstrate that RB can inhibit apoptosis independent of growth suppression
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
