Open AccessParadoxical Instability–Activity Relationship Defines a Novel Regulatory Pathway for Retinoblastoma Proteins
Author(s) -
Pankaj Acharya,
Nitin Raj,
Martin S. Buckley,
Liang Zhang,
Stephanie Duperon,
Gwyneth Williams,
R. William Henry,
David N. Arnosti
Publication year - 2010
Publication title -
molecular biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.463
H-Index - 225
eISSN - 1939-4586
pISSN - 1059-1524
DOI - 10.1091/mbc.e10-06-0520
Subject(s) - biology , corepressor , repressor , retinoblastoma protein , psychological repression , transcription factor , genetics , microbiology and biotechnology , degron , e2f , cell cycle , transcriptional regulation , retinoblastoma , dna binding protein , basic helix loop helix , cyclin dependent kinase , ubiquitin , ubiquitin ligase , gene , gene expression
The retinoblastoma (RB) transcriptional corepressor and related family of pocket proteins play central roles in cell cycle control and development, and the regulatory networks governed by these factors are frequently inactivated during tumorigenesis. During normal growth, these proteins are subject to tight control through at least two mechanisms. First, during cell cycle progression, repressor potential is down-regulated by Cdk-dependent phosphorylation, resulting in repressor dissociation from E2F family transcription factors. Second, RB proteins are subject to proteasome-mediated destruction during development. To better understand the mechanism for RB family protein instability, we characterized Rbf1 turnover in Drosophila and the protein motifs required for its destabilization. We show that specific point mutations in a conserved C-terminal instability element strongly stabilize Rbf1, but strikingly, these mutations also cripple repression activity. Rbf1 is destabilized specifically in actively proliferating tissues of the larva, indicating that controlled degradation of Rbf1 is linked to developmental signals. The positive linkage between Rbf1 activity and its destruction indicates that repressor function is governed in a manner similar to that described by the degron theory of transcriptional activation. Analogous mutations in the mammalian RB family member p107 similarly induce abnormal accumulation, indicating substantial conservation of this regulatory pathway.