More recently, Dr. Fregoso, together with graduate student Shipra Das in Krainer's lab found that SRSF1 interacts with RPL5 as part of a complex that is not involved in their respective roles in splicing or the ribosome. They showed that this complex prevents the degradation of the powerful tumor-suppressor protein p53.
Yet Krainer's team also showed that increased expression of SRSF1 in primary human fibroblast cells decreased their proliferation and triggered a cellular senescence program in which cell growth is arrested. "It's a little surprising because we've published about SRSF1 being oncogenic, and here we find it stabilizing a tumor-suppressor protein," Krainer acknowledged. "But this seems to be a theme with oncogenes: the cells try to respond to their activity by undergoing senescence," a quiescent state in which cells don't replicate.
The process of cell-cycle arrest in response to oncogenic stress is known as oncogene induced senescence (OIS) and was described at CSHL by Scott Lowe's laboratory in 1997 [link: http://www.sciencedirect.com/science/article/pii/S0092867400819029]. That discovery was the first indication that normal cells have a mechanism in place that acts to prevent transformation into a cancer cell.
Through the interaction of the splicing protein SRSF1 and the ribosomal protein RLP5 Krainer's new research also identifies a link between oncogenic stress and the ribosomal stress response. This was found to result in the activation of p53 and cell-growth arrest. "We've identified a novel mechanism by which the oncoprotein SRSF1 keeps a check on its own aberrant activity," noted Das. "The discovery of this novel role for SRSF1 enhances our understanding of how tumors arise and the pathways to transformation," added Krainer.
|Contact: Edward Brydon Ph.D.|
Cold Spring Harbor Laboratory