Related Experiment Videos
PML is induced by oncogenic ras and promotes premature senescence
G Ferbeyre1, E de Stanchina, E Querido
1Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA.
Abstract:
Oncogenic ras provokes a senescent-like arrest in human diploid fibroblasts involving the Rb and p53 tumor suppressor pathways. To further characterize this response, we compared gene expression patterns between ras-arrested and quiescent IMR90 fibroblasts. One of the genes up-regulated during ras-induced arrest was promyelocytic leukemia (PML) protein, a potential tumor suppressor that encodes a component of nuclear structures known as promyelocytic oncogenic domains (PODs). PML levels increased during both ras-induced arrest and replicative senescence, leading to a dramatic increase in the size and number of PODs. Forced PML expression was sufficient to promote premature senescence. Like oncogenic ras, PML increased the levels of p16, hypophosphorylated Rb, phosphoserine-15 p53, and expression of p53 transcriptional targets. The fraction of Rb and p53 that colocalized with PML markedly increased during ras-induced arrest, and expression of PML alone forced p53 to the PODs. E1A abolished PML-induced arrest and prevented PML induction and p53 phosphorylation in response to oncogenic ras. These results imply that PML acts with Rb and p53 to promote ras-induced senescence and provide new insights into PML regulation and activity.
Insights
Oncogenic Ras triggers a senescence-like arrest in human cells. Promyelocytic leukemia (PML) protein accumulates during this arrest, promoting senescence by interacting with Rb and p53 tumor suppressors.
Area of Science:
- Cellular senescence
- Tumor suppressor pathways
- Oncogene-induced cell cycle arrest
Background:
- Oncogenic Ras proteins are key drivers of cellular transformation.
- Ras-induced senescence involves the Rb and p53 tumor suppressor pathways.
- Promyelocytic leukemia (PML) protein is implicated in tumor suppression and nuclear organization.
Purpose of the Study:
- To characterize gene expression changes during Ras-induced senescence.
- To investigate the role of PML protein in Ras-induced cell cycle arrest.
- To elucidate the interaction between PML, Rb, and p53 in senescence.
Main Methods:
- Comparative gene expression analysis of Ras-arrested and quiescent IMR90 fibroblasts.
- Assessment of PML protein levels and promyelocytic oncogenic domain (POD) formation.
- Forced expression of PML and analysis of its effects on senescence markers.
- Co-localization studies of PML, Rb, and p53.
Main Results:
- PML protein levels and PODs increase during Ras-induced arrest and replicative senescence.
- Forced PML expression induces premature senescence.
- PML enhances Rb and p53 pathway activation, including p16 and p53 targets.
- PML, Rb, and p53 colocalize within PODs during Ras-induced arrest.
Conclusions:
- PML acts in concert with Rb and p53 to mediate Ras-induced senescence.
- PML localization to PODs is critical for its function in senescence.
- These findings offer new insights into PML regulation and its role in tumor suppression.