TORC2 regulates germinal center repression of the TCL1 oncoprotein to promote B cell development and inhibit transformation

AI Kuraishy, SW French, M Sherman… - Proceedings of the …, 2007 - National Acad Sciences
AI Kuraishy, SW French, M Sherman, M Herling, D Jones, R Wall, MA Teitell
Proceedings of the National Academy of Sciences, 2007National Acad Sciences
Aberrant expression of the TCL1 oncoprotein promotes malignant transformation of germinal
center (GC) B cells. Repression of TCL1 in GC B cells facilitates FAS-mediated apoptosis
and prevents lymphoma formation. However, the mechanism for this repression is unknown.
Here we show that the CREB coactivator TORC2 directly regulates TCL1 expression
independent of CREB Ser-133 phosphorylation and CBP/p300 recruitment. GC signaling
through CD40 or the BCR, which activates pCREB-dependent genes, caused TORC2 …
Aberrant expression of the TCL1 oncoprotein promotes malignant transformation of germinal center (GC) B cells. Repression of TCL1 in GC B cells facilitates FAS-mediated apoptosis and prevents lymphoma formation. However, the mechanism for this repression is unknown. Here we show that the CREB coactivator TORC2 directly regulates TCL1 expression independent of CREB Ser-133 phosphorylation and CBP/p300 recruitment. GC signaling through CD40 or the BCR, which activates pCREB-dependent genes, caused TORC2 phosphorylation, cytosolic emigration, and TCL1 repression. Signaling via cAMP-inducible pathways inhibited TCL1 repression and reduced apoptosis, consistent with a prosurvival role for TCL1 before GC selection and supporting an initiating role for aberrant TCL1 expression during GC lymphomagenesis. Our data indicate that a novel CREB/TORC2 regulatory mode controls the normal program of GC gene activation and repression that promotes B cell development and circumvents oncogenic progression. Our results also reconcile a paradox in which signals that activate pCREB/CBP/p300 genes concurrently repress TCL1 to initiate its silencing.
National Acad Sciences