Conserved region 2 of adenovirus E1A has a function distinct from pRb binding required to prevent cell cycle arrest by p16INK4a or p27Kip1.
Ectopic expression of the CDK inhibitors (CKIs) p16INK4a and p27Kip1 in Rat1 fibroblasts induces dephosphorylation and activation of Retinoblastoma-family proteins (pRb, p107 and p130), their association with E2F proteins, and cell cycle arrest in G1. The growth-inhibitory action of p16, in particular, is believed to be mediated essentially via pRb activation. The 12S E1A protein of human Adenovirus 5 associates with pRb-family proteins via residues in its Conserved Regions (CR) 1 and 2, in particular through the motif LXCXE in CR2. These interactions are required for E1A to prevent G1 arrest upon co-expression of CKIs. We show here that mutating either of two conserved motifs adjacent to LXCXE in CR2, GFP and SDDEDEE, also impairs the ability of E1A to overcome G1 arrest by p16 or p27. Strikingly, however, these mutations affect neither the association of E1A with pRb, p07 and p130, nor its ability to derepress E2F-1 transcriptional activity in transient transfection assays. One of the EIA mutants, however, is defective in derepressing several endogenous E2F target genes in the presence of p16 or p27. Thus, CR2 possesses an essential function besides pRb-binding. We speculate that this function might be required for the full derepression of E2F-regulated genes in their natural chromatin context.
Alevizopoulos
K
K
Swiss Institute for Experimental Cancer Research, Epalinges.
Sanchez
B
B
Amati
B
B
D017500:Adenovirus E1A Proteins / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins; D017124:Conserved Sequence; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism*; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins
D017500:Adenovirus E1A Proteins; D002352:Carrier Proteins; C493962:Cdkn1b protein, rat; D018797:Cell Cycle Proteins; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493755:E2f1 protein, rat; D008869:Microtubule-Associated Proteins; D016160:Retinoblastoma Protein; D056465:Retinoblastoma-Binding Protein 1; D050680:Transcription Factor DP1; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27