1. ¹Department of Cancer Biology and Genetics, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
2. ²Computational Biology Center, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
3. ³Department of Biochemistry, McGill University, Promenade Sir William Osler, Montreal, Quebec, Canada
4. ⁴Departments of Surgery, Neurosurgery and Neurology, Memorial Sloan–Kettering Cancer Center, New York, NY, USA
5. ⁵Brain Tumor Center, Memorial Sloan–Kettering Cancer Center, New York, NY, USA

Correspondence: Dr F Brenet, Department of Medicine, Weill Medical College of Cornell University, 1300 York Avenue, Room A635, New York, NY 10021, USA. E-mail: fab2008@med.cornell.edu

Received 4 June 2008; Revised 19 August 2008; Accepted 22 August 2008; Published online 6 October 2008.

Abstract

The Akt signaling pathway activity increases as normal tissue progresses to malignant transformation, and regulates the translation of specific messenger RNAs (mRNAs) through multiple mechanisms. We have identified one such mechanism of Akt-dependent translation control as involving the lupus autoantigen La. La is an RNA-associated protein that contains multiple trafficking elements to support the interaction with RNAs in different subcellular locations. We show here that the La protein is a direct target of the serine/threonine protein kinase Akt on threonine 301, and La nuclear export in mouse glial progenitors, as well as its association with polysomes is modulated by Akt activity. Using a functional approach to determine the network of genes affected by La in the cytoplasm by microarray analysis of polysome-bound mRNAs, we found that La binds 34% of the polysome bound mRNAs and regulates the expression of a specific pool of mRNAs under KRas/Akt activation. Therefore, La appears to be an important contributor to Akt-mediated translational regulation of these transcripts in murine glial cells.